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revision 225 by ph10, Mon Aug 20 14:38:34 2007 UTC revision 642 by ph10, Thu Jul 28 18:59:40 2011 UTC
# Line 132  an application that uses PCRE. The heade Line 132  an application that uses PCRE. The heade
132  and PCRE_MINOR to contain the major and minor release numbers for the library.  and PCRE_MINOR to contain the major and minor release numbers for the library.
133  Applications can use these to include support for different releases of PCRE.  Applications can use these to include support for different releases of PCRE.
134  .P  .P
135    In a Windows environment, if you want to statically link an application program
136    against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
137    including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
138    \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
139    \fB__declspec(dllimport)\fP, with unwanted results.
140    .P
141  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
142  and \fBpcre_exec()\fP are used for compiling and matching regular expressions  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
143  in a Perl-compatible manner. A sample program that demonstrates the simplest  in a Perl-compatible manner. A sample program that demonstrates the simplest
144  way of using them is provided in the file called \fIpcredemo.c\fP in the source  way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
145  distribution. The  source distribution. A listing of this program is given in the
146    .\" HREF
147    \fBpcredemo\fP
148    .\"
149    documentation, and the
150  .\" HREF  .\" HREF
151  \fBpcresample\fP  \fBpcresample\fP
152  .\"  .\"
153  documentation describes how to run it.  documentation describes how to compile and run it.
154  .P  .P
155  A second matching function, \fBpcre_dfa_exec()\fP, which is not  A second matching function, \fBpcre_dfa_exec()\fP, which is not
156  Perl-compatible, is also provided. This uses a different algorithm for the  Perl-compatible, is also provided. This uses a different algorithm for the
157  matching. The alternative algorithm finds all possible matches (at a given  matching. The alternative algorithm finds all possible matches (at a given
158  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
159  does not return captured substrings. A description of the two matching  lookbehind assertions). However, this algorithm does not return captured
160  algorithms and their advantages and disadvantages is given in the  substrings. A description of the two matching algorithms and their advantages
161    and disadvantages is given in the
162  .\" HREF  .\" HREF
163  \fBpcrematching\fP  \fBpcrematching\fP
164  .\"  .\"
# Line 218  points during a matching operation. Deta Line 229  points during a matching operation. Deta
229  documentation.  documentation.
230  .  .
231  .  .
232    .\" HTML <a name="newlines"></a>
233  .SH NEWLINES  .SH NEWLINES
234  .rs  .rs
235  .sp  .sp
# Line 235  The default default is LF, which is the Line 247  The default default is LF, which is the
247  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
248  matched.  matched.
249  .P  .P
250    At compile time, the newline convention can be specified by the \fIoptions\fP
251    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
252    start of the pattern itself; this overrides any other settings. See the
253    .\" HREF
254    \fBpcrepattern\fP
255    .\"
256    page for details of the special character sequences.
257    .P
258  In the PCRE documentation the word "newline" is used to mean "the character or  In the PCRE documentation the word "newline" is used to mean "the character or
259  pair of characters that indicate a line break". The choice of newline  pair of characters that indicate a line break". The choice of newline
260  convention affects the handling of the dot, circumflex, and dollar  convention affects the handling of the dot, circumflex, and dollar
261  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
262  recognized line ending sequence, the match position advancement for a  recognized line ending sequence, the match position advancement for a
263  non-anchored pattern. The choice of newline convention does not affect the  non-anchored pattern. There is more detail about this in the
264  interpretation of the \en or \er escape sequences.  .\" HTML <a href="#execoptions">
265    .\" </a>
266    section on \fBpcre_exec()\fP options
267    .\"
268    below.
269    .P
270    The choice of newline convention does not affect the interpretation of
271    the \en or \er escape sequences, nor does it affect what \eR matches, which is
272    controlled in a similar way, but by separate options.
273  .  .
274  .  .
275  .SH MULTITHREADING  .SH MULTITHREADING
# Line 300  properties is available; otherwise it is Line 328  properties is available; otherwise it is
328  .sp  .sp
329  The output is an integer whose value specifies the default character sequence  The output is an integer whose value specifies the default character sequence
330  that is recognized as meaning "newline". The four values that are supported  that is recognized as meaning "newline". The four values that are supported
331  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY. The  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
332  default should normally be the standard sequence for your operating system.  Though they are derived from ASCII, the same values are returned in EBCDIC
333    environments. The default should normally correspond to the standard sequence
334    for your operating system.
335    .sp
336      PCRE_CONFIG_BSR
337    .sp
338    The output is an integer whose value indicates what character sequences the \eR
339    escape sequence matches by default. A value of 0 means that \eR matches any
340    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
341    or CRLF. The default can be overridden when a pattern is compiled or matched.
342  .sp  .sp
343    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
344  .sp  .sp
# Line 323  documentation. Line 360  documentation.
360  .sp  .sp
361    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
362  .sp  .sp
363  The output is an integer that gives the default limit for the number of  The output is a long integer that gives the default limit for the number of
364  internal matching function calls in a \fBpcre_exec()\fP execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
365  details are given with \fBpcre_exec()\fP below.  details are given with \fBpcre_exec()\fP below.
366  .sp  .sp
367    PCRE_CONFIG_MATCH_LIMIT_RECURSION    PCRE_CONFIG_MATCH_LIMIT_RECURSION
368  .sp  .sp
369  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
370  recursion when calling the internal matching function in a \fBpcre_exec()\fP  recursion when calling the internal matching function in a \fBpcre_exec()\fP
371  execution. Further details are given with \fBpcre_exec()\fP below.  execution. Further details are given with \fBpcre_exec()\fP below.
372  .sp  .sp
# Line 364  avoiding the use of the stack. Line 401  avoiding the use of the stack.
401  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
402  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
403  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
404  \fIerrorcodeptr\fP, via which a numerical error code can be returned.  \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
405    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
406    information applies equally to \fBpcre_compile2()\fP.
407  .P  .P
408  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
409  \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 380  argument, which is an address (see below Line 419  argument, which is an address (see below
419  .P  .P
420  The \fIoptions\fP argument contains various bit settings that affect the  The \fIoptions\fP argument contains various bit settings that affect the
421  compilation. It should be zero if no options are required. The available  compilation. It should be zero if no options are required. The available
422  options are described below. Some of them, in particular, those that are  options are described below. Some of them (in particular, those that are
423  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
424  the detailed description in the  within the pattern (see the detailed description in the
425  .\" HREF  .\" HREF
426  \fBpcrepattern\fP  \fBpcrepattern\fP
427  .\"  .\"
428  documentation). For these options, the contents of the \fIoptions\fP argument  documentation). For those options that can be different in different parts of
429  specifies their initial settings at the start of compilation and execution. The  the pattern, the contents of the \fIoptions\fP argument specifies their
430  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,
431  matching as well as at compile time.  PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and
432    PCRE_NO_START_OPT options can be set at the time of matching as well as at
433    compile time.
434  .P  .P
435  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
436  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
437  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
438  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
439  not try to free it. The offset from the start of the pattern to the character  not try to free it. Normally, the offset from the start of the pattern to the
440  where the error was discovered is placed in the variable pointed to by  byte that was being processed when the error was discovered is placed in the
441  \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.  variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
442    immediate error is given). However, for an invalid UTF-8 string, the offset is
443    that of the first byte of the failing character. Also, some errors are not
444    detected until checks are carried out when the whole pattern has been scanned;
445    in these cases the offset passed back is the length of the pattern.
446    .P
447    Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
448    sometimes point into the middle of a UTF-8 character.
449  .P  .P
450  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
451  \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 444  facility, see the Line 492  facility, see the
492  .\"  .\"
493  documentation.  documentation.
494  .sp  .sp
495      PCRE_BSR_ANYCRLF
496      PCRE_BSR_UNICODE
497    .sp
498    These options (which are mutually exclusive) control what the \eR escape
499    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
500    match any Unicode newline sequence. The default is specified when PCRE is
501    built. It can be overridden from within the pattern, or by setting an option
502    when a compiled pattern is matched.
503    .sp
504    PCRE_CASELESS    PCRE_CASELESS
505  .sp  .sp
506  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 467  pattern. Line 524  pattern.
524  .sp  .sp
525    PCRE_DOTALL    PCRE_DOTALL
526  .sp  .sp
527  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
528  including those that indicate newline. Without it, a dot does not match when  any value, including one that indicates a newline. However, it only ever
529  the current position is at a newline. This option is equivalent to Perl's /s  matches one character, even if newlines are coded as CRLF. Without this option,
530  option, and it can be changed within a pattern by a (?s) option setting. A  a dot does not match when the current position is at a newline. This option is
531  negative class such as [^a] always matches newline characters, independent of  equivalent to Perl's /s option, and it can be changed within a pattern by a
532  the setting of this option.  (?s) option setting. A negative class such as [^a] always matches newline
533    characters, independent of the setting of this option.
534  .sp  .sp
535    PCRE_DUPNAMES    PCRE_DUPNAMES
536  .sp  .sp
# Line 494  unescaped # outside a character class an Line 552  unescaped # outside a character class an
552  ignored. This is equivalent to Perl's /x option, and it can be changed within a  ignored. This is equivalent to Perl's /x option, and it can be changed within a
553  pattern by a (?x) option setting.  pattern by a (?x) option setting.
554  .P  .P
555    Which characters are interpreted as newlines is controlled by the options
556    passed to \fBpcre_compile()\fP or by a special sequence at the start of the
557    pattern, as described in the section entitled
558    .\" HTML <a href="pcrepattern.html#newlines">
559    .\" </a>
560    "Newline conventions"
561    .\"
562    in the \fBpcrepattern\fP documentation. Note that the end of this type of
563    comment is a literal newline sequence in the pattern; escape sequences that
564    happen to represent a newline do not count.
565    .P
566  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
567  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. Whitespace characters
568  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
569  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( that introduces a conditional subpattern.
570  .sp  .sp
571    PCRE_EXTRA    PCRE_EXTRA
572  .sp  .sp
# Line 507  set, any backslash in a pattern that is Line 576  set, any backslash in a pattern that is
576  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
577  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
578  special meaning is treated as a literal. (Perl can, however, be persuaded to  special meaning is treated as a literal. (Perl can, however, be persuaded to
579  give a warning for this.) There are at present no other features controlled by  give an error for this, by running it with the -w option.) There are at present
580  this option. It can also be set by a (?X) option setting within a pattern.  no other features controlled by this option. It can also be set by a (?X)
581    option setting within a pattern.
582  .sp  .sp
583    PCRE_FIRSTLINE    PCRE_FIRSTLINE
584  .sp  .sp
# Line 516  If this option is set, an unanchored pat Line 586  If this option is set, an unanchored pat
586  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
587  over the newline.  over the newline.
588  .sp  .sp
589      PCRE_JAVASCRIPT_COMPAT
590    .sp
591    If this option is set, PCRE's behaviour is changed in some ways so that it is
592    compatible with JavaScript rather than Perl. The changes are as follows:
593    .P
594    (1) A lone closing square bracket in a pattern causes a compile-time error,
595    because this is illegal in JavaScript (by default it is treated as a data
596    character). Thus, the pattern AB]CD becomes illegal when this option is set.
597    .P
598    (2) At run time, a back reference to an unset subpattern group matches an empty
599    string (by default this causes the current matching alternative to fail). A
600    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
601    an "a" in the subject), whereas it fails by default, for Perl compatibility.
602    .sp
603    PCRE_MULTILINE    PCRE_MULTILINE
604  .sp  .sp
605  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 557  option, the combination may or may not b Line 641  option, the combination may or may not b
641  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
642  other combinations may yield unused numbers and cause an error.  other combinations may yield unused numbers and cause an error.
643  .P  .P
644  The only time that a line break is specially recognized when compiling a  The only time that a line break in a pattern is specially recognized when
645  pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character  compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
646  class is encountered. This indicates a comment that lasts until after the next  and so are ignored in this mode. Also, an unescaped # outside a character class
647  line break sequence. In other circumstances, line break sequences are treated  indicates a comment that lasts until after the next line break sequence. In
648  as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated  other circumstances, line break sequences in patterns are treated as literal
649  as whitespace characters and are therefore ignored.  data.
650  .P  .P
651  The newline option that is set at compile time becomes the default that is used  The newline option that is set at compile time becomes the default that is used
652  for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.  for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
# Line 575  were followed by ?: but named parenthese Line 659  were followed by ?: but named parenthese
659  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
660  in Perl.  in Perl.
661  .sp  .sp
662      NO_START_OPTIMIZE
663    .sp
664    This is an option that acts at matching time; that is, it is really an option
665    for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
666    it is remembered with the compiled pattern and assumed at matching time. For
667    details see the discussion of PCRE_NO_START_OPTIMIZE
668    .\" HTML <a href="#execoptions">
669    .\" </a>
670    below.
671    .\"
672    .sp
673      PCRE_UCP
674    .sp
675    This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
676    \ew, and some of the POSIX character classes. By default, only ASCII characters
677    are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
678    classify characters. More details are given in the section on
679    .\" HTML <a href="pcre.html#genericchartypes">
680    .\" </a>
681    generic character types
682    .\"
683    in the
684    .\" HREF
685    \fBpcrepattern\fP
686    .\"
687    page. If you set PCRE_UCP, matching one of the items it affects takes much
688    longer. The option is available only if PCRE has been compiled with Unicode
689    property support.
690    .sp
691    PCRE_UNGREEDY    PCRE_UNGREEDY
692  .sp  .sp
693  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
# Line 639  out of use. To avoid confusion, they hav Line 752  out of use. To avoid confusion, they hav
752     9  nothing to repeat     9  nothing to repeat
753    10  [this code is not in use]    10  [this code is not in use]
754    11  internal error: unexpected repeat    11  internal error: unexpected repeat
755    12  unrecognized character after (?    12  unrecognized character after (? or (?-
756    13  POSIX named classes are supported only within a class    13  POSIX named classes are supported only within a class
757    14  missing )    14  missing )
758    15  reference to non-existent subpattern    15  reference to non-existent subpattern
# Line 647  out of use. To avoid confusion, they hav Line 760  out of use. To avoid confusion, they hav
760    17  unknown option bit(s) set    17  unknown option bit(s) set
761    18  missing ) after comment    18  missing ) after comment
762    19  [this code is not in use]    19  [this code is not in use]
763    20  regular expression too large    20  regular expression is too large
764    21  failed to get memory    21  failed to get memory
765    22  unmatched parentheses    22  unmatched parentheses
766    23  internal error: code overflow    23  internal error: code overflow
# Line 676  out of use. To avoid confusion, they hav Line 789  out of use. To avoid confusion, they hav
789    46  malformed \eP or \ep sequence    46  malformed \eP or \ep sequence
790    47  unknown property name after \eP or \ep    47  unknown property name after \eP or \ep
791    48  subpattern name is too long (maximum 32 characters)    48  subpattern name is too long (maximum 32 characters)
792    49  too many named subpatterns (maximum 10,000)    49  too many named subpatterns (maximum 10000)
793    50  [this code is not in use]    50  [this code is not in use]
794    51  octal value is greater than \e377 (not in UTF-8 mode)    51  octal value is greater than \e377 (not in UTF-8 mode)
795    52  internal error: overran compiling workspace    52  internal error: overran compiling workspace
796    53  internal error: previously-checked referenced subpattern not found    53  internal error: previously-checked referenced subpattern
797            not found
798    54  DEFINE group contains more than one branch    54  DEFINE group contains more than one branch
799    55  repeating a DEFINE group is not allowed    55  repeating a DEFINE group is not allowed
800    56  inconsistent NEWLINE options"    56  inconsistent NEWLINE options
801    57  \eg is not followed by a braced name or an optionally braced    57  \eg is not followed by a braced, angle-bracketed, or quoted
802          non-zero number          name/number or by a plain number
803    58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number    58  a numbered reference must not be zero
804      59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
805      60  (*VERB) not recognized
806      61  number is too big
807      62  subpattern name expected
808      63  digit expected after (?+
809      64  ] is an invalid data character in JavaScript compatibility mode
810      65  different names for subpatterns of the same number are
811            not allowed
812      66  (*MARK) must have an argument
813      67  this version of PCRE is not compiled with PCRE_UCP support
814    .sp
815    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
816    be used if the limits were changed when PCRE was built.
817  .  .
818  .  .
819  .SH "STUDYING A PATTERN"  .SH "STUDYING A PATTERN"
# Line 705  help speed up matching, \fBpcre_study()\ Line 832  help speed up matching, \fBpcre_study()\
832  results of the study.  results of the study.
833  .P  .P
834  The returned value from \fBpcre_study()\fP can be passed directly to  The returned value from \fBpcre_study()\fP can be passed directly to
835  \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
836  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
837  described  passed; these are described
838  .\" HTML <a href="#extradata">  .\" HTML <a href="#extradata">
839  .\" </a>  .\" </a>
840  below  below
841  .\"  .\"
842  in the section on matching a pattern.  in the section on matching a pattern.
843  .P  .P
844  If studying the pattern does not produce any additional information  If studying the pattern does not produce any useful information,
845  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
846  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
847  own \fBpcre_extra\fP block.  \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
848  .P  .P
849  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
850  options are defined, and this argument should always be zero.  options are defined, and this argument should always be zero.
# Line 737  This is a typical call to \fBpcre_study\ Line 864  This is a typical call to \fBpcre_study\
864      0,              /* no options exist */      0,              /* no options exist */
865      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
866  .sp  .sp
867  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
868  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
869  bytes is created.  mean that there are any strings of that length that match, but it does
870    guarantee that no shorter strings match. The value is used by
871    \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
872    match strings that are shorter than the lower bound. You can find out the value
873    in a calling program via the \fBpcre_fullinfo()\fP function.
874    .P
875    Studying a pattern is also useful for non-anchored patterns that do not have a
876    single fixed starting character. A bitmap of possible starting bytes is
877    created. This speeds up finding a position in the subject at which to start
878    matching.
879    .P
880    The two optimizations just described can be disabled by setting the
881    PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
882    \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
883    callouts or (*MARK), and you want to make use of these facilities in cases
884    where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
885    .\" HTML <a href="#execoptions">
886    .\" </a>
887    below.
888    .\"
889  .  .
890  .  .
891  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
# Line 749  bytes is created. Line 895  bytes is created.
895  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
896  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
897  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
898  less than 128. Higher-valued codes never match escapes such as \ew or \ed, but  less than 128. By default, higher-valued codes never match escapes such as \ew
899  can be tested with \ep if PCRE is built with Unicode character property  or \ed, but they can be tested with \ep if PCRE is built with Unicode character
900  support. The use of locales with Unicode is discouraged. If you are handling  property support. Alternatively, the PCRE_UCP option can be set at compile
901  characters with codes greater than 128, you should either use UTF-8 and  time; this causes \ew and friends to use Unicode property support instead of
902  Unicode, or use locales, but not try to mix the two.  built-in tables. The use of locales with Unicode is discouraged. If you are
903    handling characters with codes greater than 128, you should either use UTF-8
904    and Unicode, or use locales, but not try to mix the two.
905  .P  .P
906  PCRE contains an internal set of tables that are used when the final argument  PCRE contains an internal set of tables that are used when the final argument
907  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
# Line 798  one in which it was compiled. Passing ta Line 946  one in which it was compiled. Passing ta
946  below in the section on matching a pattern.  below in the section on matching a pattern.
947  .  .
948  .  .
949    .\" HTML <a name="infoaboutpattern"></a>
950  .SH "INFORMATION ABOUT A PATTERN"  .SH "INFORMATION ABOUT A PATTERN"
951  .rs  .rs
952  .sp  .sp
# Line 882  table indicating a fixed set of bytes fo Line 1031  table indicating a fixed set of bytes fo
1031  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
1032  fourth argument should point to an \fBunsigned char *\fP variable.  fourth argument should point to an \fBunsigned char *\fP variable.
1033  .sp  .sp
1034      PCRE_INFO_HASCRORLF
1035    .sp
1036    Return 1 if the pattern contains any explicit matches for CR or LF characters,
1037    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1038    explicit match is either a literal CR or LF character, or \er or \en.
1039    .sp
1040    PCRE_INFO_JCHANGED    PCRE_INFO_JCHANGED
1041  .sp  .sp
1042  Return 1 if the (?J) option setting is used in the pattern, otherwise 0. The  Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1043  fourth argument should point to an \fBint\fP variable. The (?J) internal option  0. The fourth argument should point to an \fBint\fP variable. (?J) and
1044  setting changes the local PCRE_DUPNAMES option.  (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1045  .sp  .sp
1046    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1047  .sp  .sp
# Line 898  follows something of variable length. Fo Line 1053  follows something of variable length. Fo
1053  /^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
1054  is -1.  is -1.
1055  .sp  .sp
1056      PCRE_INFO_MINLENGTH
1057    .sp
1058    If the pattern was studied and a minimum length for matching subject strings
1059    was computed, its value is returned. Otherwise the returned value is -1. The
1060    value is a number of characters, not bytes (this may be relevant in UTF-8
1061    mode). The fourth argument should point to an \fBint\fP variable. A
1062    non-negative value is a lower bound to the length of any matching string. There
1063    may not be any strings of that length that do actually match, but every string
1064    that does match is at least that long.
1065    .sp
1066    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1067    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1068    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
# Line 918  entry; both of these return an \fBint\fP Line 1083  entry; both of these return an \fBint\fP
1083  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
1084  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
1085  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
1086  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated.
1087  alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of  .P
1088  their parentheses numbers. For example, consider the following pattern (assume  The names are in alphabetical order. Duplicate names may appear if (?| is used
1089  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  to create multiple groups with the same number, as described in the
1090    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1091    .\" </a>
1092    section on duplicate subpattern numbers
1093    .\"
1094    in the
1095    .\" HREF
1096    \fBpcrepattern\fP
1097    .\"
1098    page. Duplicate names for subpatterns with different numbers are permitted only
1099    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1100    table in the order in which they were found in the pattern. In the absence of
1101    (?| this is the order of increasing number; when (?| is used this is not
1102    necessarily the case because later subpatterns may have lower numbers.
1103    .P
1104    As a simple example of the name/number table, consider the following pattern
1105    (assume PCRE_EXTENDED is set, so white space - including newlines - is
1106    ignored):
1107  .sp  .sp
1108  .\" JOIN  .\" JOIN
1109    (?<date> (?<year>(\ed\ed)?\ed\ed) -    (?<date> (?<year>(\ed\ed)?\ed\ed) -
# Line 942  different for each compiled pattern. Line 1124  different for each compiled pattern.
1124  .sp  .sp
1125    PCRE_INFO_OKPARTIAL    PCRE_INFO_OKPARTIAL
1126  .sp  .sp
1127  Return 1 if the pattern can be used for partial matching, otherwise 0. The  Return 1 if the pattern can be used for partial matching with
1128  fourth argument should point to an \fBint\fP variable. The  \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1129    \fBint\fP variable. From release 8.00, this always returns 1, because the
1130    restrictions that previously applied to partial matching have been lifted. The
1131  .\" HREF  .\" HREF
1132  \fBpcrepartial\fP  \fBpcrepartial\fP
1133  .\"  .\"
1134  documentation lists the restrictions that apply to patterns when partial  documentation gives details of partial matching.
 matching is used.  
1135  .sp  .sp
1136    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1137  .sp  .sp
# Line 985  variable. Line 1168  variable.
1168  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
1169  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
1170  \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
1171  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
1172    study data, zero is returned. The fourth argument should point to a
1173  \fBsize_t\fP variable.  \fBsize_t\fP variable.
1174  .  .
1175  .  .
# Line 1047  is different. (This seems a highly unlik Line 1231  is different. (This seems a highly unlik
1231  .P  .P
1232  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
1233  compiled pattern, which is passed in the \fIcode\fP argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1234  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
1235  \fIextra\fP argument. This function is the main matching facility of the  \fIextra\fP argument. This function is the main matching facility of the
1236  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
1237  also an alternative matching function, which is described  also an alternative matching function, which is described
# Line 1097  fields (not necessarily in this order): Line 1281  fields (not necessarily in this order):
1281    unsigned long int \fImatch_limit_recursion\fP;    unsigned long int \fImatch_limit_recursion\fP;
1282    void *\fIcallout_data\fP;    void *\fIcallout_data\fP;
1283    const unsigned char *\fItables\fP;    const unsigned char *\fItables\fP;
1284      unsigned char **\fImark\fP;
1285  .sp  .sp
1286  The \fIflags\fP field is a bitmap that specifies which of the other fields  The \fIflags\fP field is a bitmap that specifies which of the other fields
1287  are set. The flag bits are:  are set. The flag bits are:
# Line 1106  are set. The flag bits are: Line 1291  are set. The flag bits are:
1291    PCRE_EXTRA_MATCH_LIMIT_RECURSION    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1292    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1293    PCRE_EXTRA_TABLES    PCRE_EXTRA_TABLES
1294      PCRE_EXTRA_MARK
1295  .sp  .sp
1296  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1297  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
# Line 1115  the block by setting the other fields an Line 1301  the block by setting the other fields an
1301  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
1302  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,
1303  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
1304  classic example is the use of nested unlimited repeats.  classic example is a pattern that uses nested unlimited repeats.
1305  .P  .P
1306  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1307  (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 1148  with a \fBpcre_extra\fP block in which \ Line 1334  with a \fBpcre_extra\fP block in which \
1334  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
1335  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1336  .P  .P
1337  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,
1338  which is described in the  and is described in the
1339  .\" HREF  .\" HREF
1340  \fBpcrecallout\fP  \fBpcrecallout\fP
1341  .\"  .\"
# Line 1168  called. See the Line 1354  called. See the
1354  \fBpcreprecompile\fP  \fBpcreprecompile\fP
1355  .\"  .\"
1356  documentation for a discussion of saving compiled patterns for later use.  documentation for a discussion of saving compiled patterns for later use.
1357    .P
1358    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1359    be set to point to a \fBchar *\fP variable. If the pattern contains any
1360    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1361    a name to pass back, a pointer to the name string (zero terminated) is placed
1362    in the variable pointed to by the \fImark\fP field. The names are within the
1363    compiled pattern; if you wish to retain such a name you must copy it before
1364    freeing the memory of a compiled pattern. If there is no name to pass back, the
1365    variable pointed to by the \fImark\fP field set to NULL. For details of the
1366    backtracking control verbs, see the section entitled
1367    .\" HTML <a href="pcrepattern#backtrackcontrol">
1368    .\" </a>
1369    "Backtracking control"
1370    .\"
1371    in the
1372    .\" HREF
1373    \fBpcrepattern\fP
1374    .\"
1375    documentation.
1376    .
1377  .  .
1378    .\" HTML <a name="execoptions"></a>
1379  .SS "Option bits for \fBpcre_exec()\fP"  .SS "Option bits for \fBpcre_exec()\fP"
1380  .rs  .rs
1381  .sp  .sp
1382  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
1383  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,
1384  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1385    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1386    PCRE_PARTIAL_HARD.
1387  .sp  .sp
1388    PCRE_ANCHORED    PCRE_ANCHORED
1389  .sp  .sp
# Line 1183  matching position. If a pattern was comp Line 1392  matching position. If a pattern was comp
1392  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
1393  matching time.  matching time.
1394  .sp  .sp
1395      PCRE_BSR_ANYCRLF
1396      PCRE_BSR_UNICODE
1397    .sp
1398    These options (which are mutually exclusive) control what the \eR escape
1399    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1400    match any Unicode newline sequence. These options override the choice that was
1401    made or defaulted when the pattern was compiled.
1402    .sp
1403    PCRE_NEWLINE_CR    PCRE_NEWLINE_CR
1404    PCRE_NEWLINE_LF    PCRE_NEWLINE_LF
1405    PCRE_NEWLINE_CRLF    PCRE_NEWLINE_CRLF
# Line 1194  the pattern was compiled. For details, s Line 1411  the pattern was compiled. For details, s
1411  \fBpcre_compile()\fP above. During matching, the newline choice affects the  \fBpcre_compile()\fP above. During matching, the newline choice affects the
1412  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1413  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
1414  pattern. When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is  pattern.
1415  set, and a match attempt fails when the current position is at a CRLF sequence,  .P
1416  the match position is advanced by two characters instead of one, in other  When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1417  words, to after the CRLF.  match attempt for an unanchored pattern fails when the current position is at a
1418  .P  CRLF sequence, and the pattern contains no explicit matches for CR or LF
1419  Anomalous effects can occur when CRLF is a valid newline sequence and explicit  characters, the match position is advanced by two characters instead of one, in
1420  \er or \en escapes appear in the pattern. For example, the string "\er\enA"  other words, to after the CRLF.
1421  matches the unanchored pattern \enA but not [X\en]A. This happens because, in  .P
1422  the first case, PCRE knows that the match must start with \en, and so it skips  The above rule is a compromise that makes the most common cases work as
1423  there before trying to match. In the second case, it has no knowledge about the  expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1424  starting character, so it starts matching at the beginning of the string, and  set), it does not match the string "\er\enA" because, after failing at the
1425  on failing, skips over the CRLF as described above. However, if the pattern is  start, it skips both the CR and the LF before retrying. However, the pattern
1426  studied, the match succeeds, because then PCRE once again knows where to start.  [\er\en]A does match that string, because it contains an explicit CR or LF
1427    reference, and so advances only by one character after the first failure.
1428    .P
1429    An explicit match for CR of LF is either a literal appearance of one of those
1430    characters, or one of the \er or \en escape sequences. Implicit matches such as
1431    [^X] do not count, nor does \es (which includes CR and LF in the characters
1432    that it matches).
1433    .P
1434    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1435    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1436  .sp  .sp
1437    PCRE_NOTBOL    PCRE_NOTBOL
1438  .sp  .sp
# Line 1232  match the empty string, the entire match Line 1458  match the empty string, the entire match
1458  .sp  .sp
1459    a?b?    a?b?
1460  .sp  .sp
1461  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
1462  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
1463  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".
1464  .P  .sp
1465  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1466  of a pattern match of the empty string within its \fBsplit()\fP function, and  .sp
1467  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
1468  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
1469  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the  can occur only if the pattern contains \eK.
1470  starting offset (see below) and trying an ordinary match again. There is some  .P
1471  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
1472    does make a special case of a pattern match of the empty string within its
1473    \fBsplit()\fP function, and when using the /g modifier. It is possible to
1474    emulate Perl's behaviour after matching a null string by first trying the match
1475    again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1476    if that fails, by advancing the starting offset (see below) and trying an
1477    ordinary match again. There is some code that demonstrates how to do this in
1478    the
1479    .\" HREF
1480    \fBpcredemo\fP
1481    .\"
1482    sample program. In the most general case, you have to check to see if the
1483    newline convention recognizes CRLF as a newline, and if so, and the current
1484    character is CR followed by LF, advance the starting offset by two characters
1485    instead of one.
1486    .sp
1487      PCRE_NO_START_OPTIMIZE
1488    .sp
1489    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1490    a match, in order to speed up the process. For example, if it is known that an
1491    unanchored match must start with a specific character, it searches the subject
1492    for that character, and fails immediately if it cannot find it, without
1493    actually running the main matching function. This means that a special item
1494    such as (*COMMIT) at the start of a pattern is not considered until after a
1495    suitable starting point for the match has been found. When callouts or (*MARK)
1496    items are in use, these "start-up" optimizations can cause them to be skipped
1497    if the pattern is never actually used. The start-up optimizations are in effect
1498    a pre-scan of the subject that takes place before the pattern is run.
1499    .P
1500    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1501    causing performance to suffer, but ensuring that in cases where the result is
1502    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1503    are considered at every possible starting position in the subject string. If
1504    PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1505    time.
1506    .P
1507    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1508    Consider the pattern
1509    .sp
1510      (*COMMIT)ABC
1511    .sp
1512    When this is compiled, PCRE records the fact that a match must start with the
1513    character "A". Suppose the subject string is "DEFABC". The start-up
1514    optimization scans along the subject, finds "A" and runs the first match
1515    attempt from there. The (*COMMIT) item means that the pattern must match the
1516    current starting position, which in this case, it does. However, if the same
1517    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1518    subject string does not happen. The first match attempt is run starting from
1519    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1520    the overall result is "no match". If the pattern is studied, more start-up
1521    optimizations may be used. For example, a minimum length for the subject may be
1522    recorded. Consider the pattern
1523    .sp
1524      (*MARK:A)(X|Y)
1525    .sp
1526    The minimum length for a match is one character. If the subject is "ABC", there
1527    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1528    If the pattern is studied, the final attempt does not take place, because PCRE
1529    knows that the subject is too short, and so the (*MARK) is never encountered.
1530    In this case, studying the pattern does not affect the overall match result,
1531    which is still "no match", but it does affect the auxiliary information that is
1532    returned.
1533  .sp  .sp
1534    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
1535  .sp  .sp
# Line 1260  in the main Line 1547  in the main
1547  \fBpcre\fP  \fBpcre\fP
1548  .\"  .\"
1549  page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns  page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1550  the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,  the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1551  PCRE_ERROR_BADUTF8_OFFSET is returned.  a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
1552    both cases, information about the precise nature of the error may also be
1553    returned (see the descriptions of these errors in the section entitled \fIError
1554    return values from\fP \fBpcre_exec()\fP
1555    .\" HTML <a href="#errorlist">
1556    .\" </a>
1557    below).
1558    .\"
1559    If \fIstartoffset\fP contains a value that does not point to the start of a
1560    UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1561    returned.
1562  .P  .P
1563  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
1564  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
1565  calling \fBpcre_exec()\fP. You might want to do this for the second and  calling \fBpcre_exec()\fP. You might want to do this for the second and
1566  subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find  subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1567  all the matches in a single subject string. However, you should be sure that  all the matches in a single subject string. However, you should be sure that
1568  the value of \fIstartoffset\fP points to the start of a UTF-8 character. When  the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
1569  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a  end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1570  subject, or a value of \fIstartoffset\fP that does not point to the start of a  invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
1571  UTF-8 character, is undefined. Your program may crash.  undefined. Your program may crash.
1572  .sp  .sp
1573    PCRE_PARTIAL    PCRE_PARTIAL_HARD
1574  .sp    PCRE_PARTIAL_SOFT
1575  This option turns on the partial matching feature. If the subject string fails  .sp
1576  to match the pattern, but at some point during the matching process the end of  These options turn on the partial matching feature. For backwards
1577  the subject was reached (that is, the subject partially matches the pattern and  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1578  the failure to match occurred only because there were not enough subject  occurs if the end of the subject string is reached successfully, but there are
1579  characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of  not enough subject characters to complete the match. If this happens when
1580  PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what  PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1581  may appear in the pattern. These are discussed in the  testing any remaining alternatives. Only if no complete match can be found is
1582    PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1583    PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1584    but only if no complete match can be found.
1585    .P
1586    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1587    partial match is found, \fBpcre_exec()\fP immediately returns
1588    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1589    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1590    important that an alternative complete match.
1591    .P
1592    In both cases, the portion of the string that was inspected when the partial
1593    match was found is set as the first matching string. There is a more detailed
1594    discussion of partial and multi-segment matching, with examples, in the
1595  .\" HREF  .\" HREF
1596  \fBpcrepartial\fP  \fBpcrepartial\fP
1597  .\"  .\"
1598  documentation.  documentation.
1599  .  .
1600    .
1601  .SS "The string to be matched by \fBpcre_exec()\fP"  .SS "The string to be matched by \fBpcre_exec()\fP"
1602  .rs  .rs
1603  .sp  .sp
1604  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
1605  \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
1606  \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a  in \fIstartoffset\fP. If this is negative or greater than the length of the
1607  UTF-8 character. Unlike the pattern string, the subject may contain binary zero  subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1608  bytes. When the starting offset is zero, the search for a match starts at the  offset is zero, the search for a match starts at the beginning of the subject,
1609  beginning of the subject, and this is by far the most common case.  and this is by far the most common case. In UTF-8 mode, the byte offset must
1610    point to the start of a UTF-8 character (or the end of the subject). Unlike the
1611    pattern string, the subject may contain binary zero bytes.
1612  .P  .P
1613  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
1614  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 1315  start of the subject, which is deemed to Line 1628  start of the subject, which is deemed to
1628  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
1629  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.
1630  .P  .P
1631    Finding all the matches in a subject is tricky when the pattern can match an
1632    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1633    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1634    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1635    and trying an ordinary match again. There is some code that demonstrates how to
1636    do this in the
1637    .\" HREF
1638    \fBpcredemo\fP
1639    .\"
1640    sample program. In the most general case, you have to check to see if the
1641    newline convention recognizes CRLF as a newline, and if so, and the current
1642    character is CR followed by LF, advance the starting offset by two characters
1643    instead of one.
1644    .P
1645  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
1646  attempt to match at the given offset is made. This can only succeed if the  attempt to match at the given offset is made. This can only succeed if the
1647  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.
1648  .  .
1649    .
1650  .SS "How \fBpcre_exec()\fP returns captured substrings"  .SS "How \fBpcre_exec()\fP returns captured substrings"
1651  .rs  .rs
1652  .sp  .sp
# Line 1329  pattern. Following the usage in Jeffrey Line 1657  pattern. Following the usage in Jeffrey
1657  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
1658  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1659  .P  .P
1660  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
1661  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
1662  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
1663  this argument is NOT the size of \fIovector\fP in bytes.  argument is NOT the size of \fIovector\fP in bytes.
1664  .P  .P
1665  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,
1666  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
1667  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1668  and is not available for passing back information. The length passed in  and is not available for passing back information. The number passed in
1669  \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
1670  rounded down.  rounded down.
1671  .P  .P
1672  When a match is successful, information about captured substrings is returned  When a match is successful, information about captured substrings is returned
1673  in pairs of integers, starting at the beginning of \fIovector\fP, and  in pairs of integers, starting at the beginning of \fIovector\fP, and
1674  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
1675  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
1676  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
1677  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
1678  subject string matched by the entire pattern. The next pair is used for the  mode. They are not character counts.
1679  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP  .P
1680  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
1681  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
1682  capturing subpatterns, the return value from a successful match is 1,  used for the first capturing subpattern, and so on. The value returned by
1683  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.
1684    For example, if two substrings have been captured, the returned value is 3. If
1685    there are no capturing subpatterns, the return value from a successful match is
1686    1, indicating that just the first pair of offsets has been set.
1687  .P  .P
1688  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
1689  string that it matched that is returned.  string that it matched that is returned.
1690  .P  .P
1691  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
1692  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
1693  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,
1694  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
1695  \fIovecsize\fP as zero. However, if the pattern contains back references and  \fIovecsize\fP as zero. However, if the pattern contains back references and
1696  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
1697  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
1698  advisable to supply an \fIovector\fP.  advisable to supply an \fIovector\fP.
1699  .P  .P
1700  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
1701  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1702  \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
1703  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 1382  Offset values that correspond to unused Line 1713  Offset values that correspond to unused
1713  expression are also set to -1. For example, if the string "abc" is matched  expression are also set to -1. For example, if the string "abc" is matched
1714  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1715  return from the function is 2, because the highest used capturing subpattern  return from the function is 2, because the highest used capturing subpattern
1716  number is 1. However, you can refer to the offsets for the second and third  number is 1, and the offsets for for the second and third capturing subpatterns
1717  capturing subpatterns if you wish (assuming the vector is large enough, of  (assuming the vector is large enough, of course) are set to -1.
1718  course).  .P
1719    \fBNote\fP: Elements of \fIovector\fP that do not correspond to capturing
1720    parentheses in the pattern are never changed. That is, if a pattern contains
1721    \fIn\fP capturing parentheses, no more than \fIovector[0]\fP to
1722    \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other elements retain
1723    whatever values they previously had.
1724  .P  .P
1725  Some convenience functions are provided for extracting the captured substrings  Some convenience functions are provided for extracting the captured substrings
1726  as separate strings. These are described below.  as separate strings. These are described below.
1727  .  .
1728    .
1729  .\" HTML <a name="errorlist"></a>  .\" HTML <a name="errorlist"></a>
1730  .SS "Error return values from \fBpcre_exec()\fP"  .SS "Error return values from \fBpcre_exec()\fP"
1731  .rs  .rs
# Line 1430  If a pattern contains back references, b Line 1767  If a pattern contains back references, b
1767  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
1768  call via \fBpcre_malloc()\fP fails, this error is given. The memory is  call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1769  automatically freed at the end of matching.  automatically freed at the end of matching.
1770    .P
1771    This error is also given if \fBpcre_stack_malloc()\fP fails in
1772    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1773    \fB--disable-stack-for-recursion\fP.
1774  .sp  .sp
1775    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1776  .sp  .sp
# Line 1454  documentation for details. Line 1795  documentation for details.
1795  .sp  .sp
1796    PCRE_ERROR_BADUTF8        (-10)    PCRE_ERROR_BADUTF8        (-10)
1797  .sp  .sp
1798  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,
1799    and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
1800    (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
1801    UTF-8 character is placed in the first element, and a reason code is placed in
1802    the second element. The reason codes are listed in the
1803    .\" HTML <a href="#badutf8reasons">
1804    .\" </a>
1805    following section.
1806    .\"
1807    For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
1808    truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
1809    PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
1810  .sp  .sp
1811    PCRE_ERROR_BADUTF8_OFFSET (-11)    PCRE_ERROR_BADUTF8_OFFSET (-11)
1812  .sp  .sp
1813  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
1814  of \fIstartoffset\fP 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
1815    \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
1816    end of the subject.
1817  .sp  .sp
1818    PCRE_ERROR_PARTIAL        (-12)    PCRE_ERROR_PARTIAL        (-12)
1819  .sp  .sp
# Line 1471  documentation for details of partial mat Line 1825  documentation for details of partial mat
1825  .sp  .sp
1826    PCRE_ERROR_BADPARTIAL     (-13)    PCRE_ERROR_BADPARTIAL     (-13)
1827  .sp  .sp
1828  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
1829  are not supported for partial matching. See the  option was used with a compiled pattern containing items that were not
1830  .\" HREF  supported for partial matching. From release 8.00 onwards, there are no
1831  \fBpcrepartial\fP  restrictions on partial matching.
 .\"  
 documentation for details of partial matching.  
1832  .sp  .sp
1833    PCRE_ERROR_INTERNAL       (-14)    PCRE_ERROR_INTERNAL       (-14)
1834  .sp  .sp
# Line 1496  description above. Line 1848  description above.
1848    PCRE_ERROR_BADNEWLINE     (-23)    PCRE_ERROR_BADNEWLINE     (-23)
1849  .sp  .sp
1850  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1851    .sp
1852      PCRE_ERROR_BADOFFSET      (-24)
1853    .sp
1854    The value of \fIstartoffset\fP was negative or greater than the length of the
1855    subject, that is, the value in \fIlength\fP.
1856    .sp
1857      PCRE_ERROR_SHORTUTF8      (-25)
1858    .sp
1859    This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
1860    ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
1861    Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
1862    fact sufficient to detect this case, but this special error code for
1863    PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
1864    retained for backwards compatibility.
1865    .sp
1866      PCRE_ERROR_RECURSELOOP    (-26)
1867    .sp
1868    This error is returned when \fBpcre_exec()\fP detects a recursion loop within
1869    the pattern. Specifically, it means that either the whole pattern or a
1870    subpattern has been called recursively for the second time at the same position
1871    in the subject string. Some simple patterns that might do this are detected and
1872    faulted at compile time, but more complicated cases, in particular mutual
1873    recursions between two different subpatterns, cannot be detected until run
1874    time.
1875  .P  .P
1876  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1877  .  .
1878  .  .
1879    .\" HTML <a name="badutf8reasons"></a>
1880    .SS "Reason codes for invalid UTF-8 strings"
1881    .rs
1882    .sp
1883    When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
1884    PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
1885    least 2, the offset of the start of the invalid UTF-8 character is placed in
1886    the first output vector element (\fIovector[0]\fP) and a reason code is placed
1887    in the second element (\fIovector[1]\fP). The reason codes are given names in
1888    the \fBpcre.h\fP header file:
1889    .sp
1890      PCRE_UTF8_ERR1
1891      PCRE_UTF8_ERR2
1892      PCRE_UTF8_ERR3
1893      PCRE_UTF8_ERR4
1894      PCRE_UTF8_ERR5
1895    .sp
1896    The string ends with a truncated UTF-8 character; the code specifies how many
1897    bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
1898    no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
1899    allows for up to 6 bytes, and this is checked first; hence the possibility of
1900    4 or 5 missing bytes.
1901    .sp
1902      PCRE_UTF8_ERR6
1903      PCRE_UTF8_ERR7
1904      PCRE_UTF8_ERR8
1905      PCRE_UTF8_ERR9
1906      PCRE_UTF8_ERR10
1907    .sp
1908    The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
1909    character do not have the binary value 0b10 (that is, either the most
1910    significant bit is 0, or the next bit is 1).
1911    .sp
1912      PCRE_UTF8_ERR11
1913      PCRE_UTF8_ERR12
1914    .sp
1915    A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
1916    these code points are excluded by RFC 3629.
1917    .sp
1918      PCRE_UTF8_ERR13
1919    .sp
1920    A 4-byte character has a value greater than 0x10fff; these code points are
1921    excluded by RFC 3629.
1922    .sp
1923      PCRE_UTF8_ERR14
1924    .sp
1925    A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
1926    code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
1927    from UTF-8.
1928    .sp
1929      PCRE_UTF8_ERR15
1930      PCRE_UTF8_ERR16
1931      PCRE_UTF8_ERR17
1932      PCRE_UTF8_ERR18
1933      PCRE_UTF8_ERR19
1934    .sp
1935    A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
1936    value that can be represented by fewer bytes, which is invalid. For example,
1937    the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
1938    one byte.
1939    .sp
1940      PCRE_UTF8_ERR20
1941    .sp
1942    The two most significant bits of the first byte of a character have the binary
1943    value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
1944    byte can only validly occur as the second or subsequent byte of a multi-byte
1945    character.
1946    .sp
1947      PCRE_UTF8_ERR21
1948    .sp
1949    The first byte of a character has the value 0xfe or 0xff. These values can
1950    never occur in a valid UTF-8 string.
1951    .
1952    .
1953  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1954  .rs  .rs
1955  .sp  .sp
# Line 1646  These functions call \fBpcre_get_stringn Line 2096  These functions call \fBpcre_get_stringn
2096  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2097  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2098  the behaviour may not be what you want (see the next section).  the behaviour may not be what you want (see the next section).
2099  .  .P
2100    \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2101    subpatterns with the same number, as described in the
2102    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2103    .\" </a>
2104    section on duplicate subpattern numbers
2105    .\"
2106    in the
2107    .\" HREF
2108    \fBpcrepattern\fP
2109    .\"
2110    page, you cannot use names to distinguish the different subpatterns, because
2111    names are not included in the compiled code. The matching process uses only
2112    numbers. For this reason, the use of different names for subpatterns of the
2113    same number causes an error at compile time.
2114  .  .
2115  .SH "DUPLICATE SUBPATTERN NAMES"  .SH "DUPLICATE SUBPATTERN NAMES"
2116  .rs  .rs
# Line 1656  the behaviour may not be what you want ( Line 2120  the behaviour may not be what you want (
2120  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2121  .PP  .PP
2122  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
2123  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
2124  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
2125  example is shown in the  such subpatterns are named, they are required to use the same names.)
2126    .P
2127    Normally, patterns with duplicate names are such that in any one match, only
2128    one of the named subpatterns participates. An example is shown in the
2129  .\" HREF  .\" HREF
2130  \fBpcrepattern\fP  \fBpcrepattern\fP
2131  .\"  .\"
# Line 1678  fourth are pointers to variables which a Line 2145  fourth are pointers to variables which a
2145  has run, they point to the first and last entries in the name-to-number table  has run, they point to the first and last entries in the name-to-number table
2146  for the given name. The function itself returns the length of each entry, or  for the given name. The function itself returns the length of each entry, or
2147  PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is  PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2148  described above in the section entitled \fIInformation about a pattern\fP.  described above in the section entitled \fIInformation about a pattern\fP
2149    .\" HTML <a href="#infoaboutpattern">
2150    .\" </a>
2151    above.
2152    .\"
2153  Given all the relevant entries for the name, you can extract each of their  Given all the relevant entries for the name, you can extract each of their
2154  numbers, and hence the captured data, if any.  numbers, and hence the captured data, if any.
2155  .  .
# Line 1722  a compiled pattern, using a matching alg Line 2193  a compiled pattern, using a matching alg
2193  just once, and does not backtrack. This has different characteristics to the  just once, and does not backtrack. This has different characteristics to the
2194  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
2195  patterns are not supported. Nevertheless, there are times when this kind of  patterns are not supported. Nevertheless, there are times when this kind of
2196  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
2197  the  list of features that \fBpcre_dfa_exec()\fP does not support, see the
2198  .\" HREF  .\" HREF
2199  \fBpcrematching\fP  \fBpcrematching\fP
2200  .\"  .\"
# Line 1762  Here is an example of a simple call to \ Line 2233  Here is an example of a simple call to \
2233  .sp  .sp
2234  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
2235  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,
2236  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2237  PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are  PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2238  the same as for \fBpcre_exec()\fP, so their description is not repeated here.  PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2239  .sp  All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2240    PCRE_PARTIAL  so their description is not repeated here.
2241  .sp  .sp
2242  This has the same general effect as it does for \fBpcre_exec()\fP, but the    PCRE_PARTIAL_HARD
2243  details are slightly different. When PCRE_PARTIAL is set for    PCRE_PARTIAL_SOFT
2244  \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into  .sp
2245  PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no  These have the same general effect as they do for \fBpcre_exec()\fP, but the
2246  complete matches, but there is still at least one matching possibility. The  details are slightly different. When PCRE_PARTIAL_HARD is set for
2247  portion of the string that provided the partial match is set as the first  \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2248  matching string.  is reached and there is still at least one matching possibility that requires
2249    additional characters. This happens even if some complete matches have also
2250    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2251    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2252    there have been no complete matches, but there is still at least one matching
2253    possibility. The portion of the string that was inspected when the longest
2254    partial match was found is set as the first matching string in both cases.
2255    There is a more detailed discussion of partial and multi-segment matching, with
2256    examples, in the
2257    .\" HREF
2258    \fBpcrepartial\fP
2259    .\"
2260    documentation.
2261  .sp  .sp
2262    PCRE_DFA_SHORTEST    PCRE_DFA_SHORTEST
2263  .sp  .sp
# Line 1785  matching point in the subject string. Line 2268  matching point in the subject string.
2268  .sp  .sp
2269    PCRE_DFA_RESTART    PCRE_DFA_RESTART
2270  .sp  .sp
2271  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
2272  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
2273  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
2274  option requests this action; when it is set, the \fIworkspace\fP and  \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2275  \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
2276  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  
2277  .\" HREF  .\" HREF
2278  \fBpcrepartial\fP  \fBpcrepartial\fP
2279  .\"  .\"
2280  documentation.  documentation.
2281  .  .
2282    .
2283  .SS "Successful returns from \fBpcre_dfa_exec()\fP"  .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2284  .rs  .rs
2285  .sp  .sp
# Line 1830  matching string is given first. If there Line 2313  matching string is given first. If there
2313  \fIovector\fP, the yield of the function is zero, and the vector is filled with  \fIovector\fP, the yield of the function is zero, and the vector is filled with
2314  the longest matches.  the longest matches.
2315  .  .
2316    .
2317  .SS "Error returns from \fBpcre_dfa_exec()\fP"  .SS "Error returns from \fBpcre_dfa_exec()\fP"
2318  .rs  .rs
2319  .sp  .sp
# Line 1895  Cambridge CB2 3QH, England. Line 2379  Cambridge CB2 3QH, England.
2379  .rs  .rs
2380  .sp  .sp
2381  .nf  .nf
2382  Last updated: 20 August 2007  Last updated: 28 July 2011
2383  Copyright (c) 1997-2007 University of Cambridge.  Copyright (c) 1997-2011 University of Cambridge.
2384  .fi  .fi

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