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revision 172 by ph10, Tue Jun 5 10:40:13 2007 UTC revision 579 by ph10, Wed Nov 24 17:39:25 2010 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. The offset from the start of the pattern to the byte that
440  where the error was discovered is placed in the variable pointed to by  was being processed when the error was discovered is placed in the variable
441  \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.  pointed to by \fIerroffset\fP, which must not be NULL. If it is, an immediate
442    error is given. Some errors are not detected until checks are carried out when
443    the whole pattern has been scanned; in this case the offset is set to the end
444    of the pattern.
445    .P
446    Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
447    point into the middle of a UTF-8 character (for example, when
448    PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
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
556    is controlled by the options passed to \fBpcre_compile()\fP or by a special
557    sequence at the start of the 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 601  page. Line 714  page.
714    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
715  .sp  .sp
716  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
717  automatically checked. If an invalid UTF-8 sequence of bytes is found,  automatically checked. There is a discussion about the
718  \fBpcre_compile()\fP returns an error. If you already know that your pattern is  .\" HTML <a href="pcre.html#utf8strings">
719  valid, and you want to skip this check for performance reasons, you can set the  .\" </a>
720  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  validity of UTF-8 strings
721  UTF-8 string as a pattern is undefined. It may cause your program to crash.  .\"
722  Note that this option can also be passed to \fBpcre_exec()\fP and  in the main
723  \fBpcre_dfa_exec()\fP, to suppress the UTF-8 validity checking of subject  .\" HREF
724  strings.  \fBpcre\fP
725    .\"
726    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
727    returns an error. If you already know that your pattern is valid, and you want
728    to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
729    option. When it is set, the effect of passing an invalid UTF-8 string as a
730    pattern is undefined. It may cause your program to crash. Note that this option
731    can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
732    the UTF-8 validity checking of subject strings.
733  .  .
734  .  .
735  .SH "COMPILATION ERROR CODES"  .SH "COMPILATION ERROR CODES"
# Line 631  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 639  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 648  out of use. To avoid confusion, they hav Line 769  out of use. To avoid confusion, they hav
769    26  malformed number or name after (?(    26  malformed number or name after (?(
770    27  conditional group contains more than two branches    27  conditional group contains more than two branches
771    28  assertion expected after (?(    28  assertion expected after (?(
772    29  (?R or (?digits must be followed by )    29  (?R or (?[+-]digits must be followed by )
773    30  unknown POSIX class name    30  unknown POSIX class name
774    31  POSIX collating elements are not supported    31  POSIX collating elements are not supported
775    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 668  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  repeated subpattern is too long    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, angle-bracketed, or quoted
802            name/number or by a plain number
803      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 694  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 726  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 738  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 871  table indicating a fixed set of bytes fo Line 1030  table indicating a fixed set of bytes fo
1030  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
1031  fourth argument should point to an \fBunsigned char *\fP variable.  fourth argument should point to an \fBunsigned char *\fP variable.
1032  .sp  .sp
1033      PCRE_INFO_HASCRORLF
1034    .sp
1035    Return 1 if the pattern contains any explicit matches for CR or LF characters,
1036    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1037    explicit match is either a literal CR or LF character, or \er or \en.
1038    .sp
1039    PCRE_INFO_JCHANGED    PCRE_INFO_JCHANGED
1040  .sp  .sp
1041  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
1042  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
1043  setting changes the local PCRE_DUPNAMES value.  (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1044  .sp  .sp
1045    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1046  .sp  .sp
# Line 887  follows something of variable length. Fo Line 1052  follows something of variable length. Fo
1052  /^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
1053  is -1.  is -1.
1054  .sp  .sp
1055      PCRE_INFO_MINLENGTH
1056    .sp
1057    If the pattern was studied and a minimum length for matching subject strings
1058    was computed, its value is returned. Otherwise the returned value is -1. The
1059    value is a number of characters, not bytes (this may be relevant in UTF-8
1060    mode). The fourth argument should point to an \fBint\fP variable. A
1061    non-negative value is a lower bound to the length of any matching string. There
1062    may not be any strings of that length that do actually match, but every string
1063    that does match is at least that long.
1064    .sp
1065    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1066    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1067    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
# Line 907  entry; both of these return an \fBint\fP Line 1082  entry; both of these return an \fBint\fP
1082  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
1083  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
1084  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
1085  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated.
1086  alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of  .P
1087  their parentheses numbers. For example, consider the following pattern (assume  The names are in alphabetical order. Duplicate names may appear if (?| is used
1088  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  to create multiple groups with the same number, as described in the
1089    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1090    .\" </a>
1091    section on duplicate subpattern numbers
1092    .\"
1093    in the
1094    .\" HREF
1095    \fBpcrepattern\fP
1096    .\"
1097    page. Duplicate names for subpatterns with different numbers are permitted only
1098    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1099    table in the order in which they were found in the pattern. In the absence of
1100    (?| this is the order of increasing number; when (?| is used this is not
1101    necessarily the case because later subpatterns may have lower numbers.
1102    .P
1103    As a simple example of the name/number table, consider the following pattern
1104    (assume PCRE_EXTENDED is set, so white space - including newlines - is
1105    ignored):
1106  .sp  .sp
1107  .\" JOIN  .\" JOIN
1108    (?<date> (?<year>(\ed\ed)?\ed\ed) -    (?<date> (?<year>(\ed\ed)?\ed\ed) -
# Line 931  different for each compiled pattern. Line 1123  different for each compiled pattern.
1123  .sp  .sp
1124    PCRE_INFO_OKPARTIAL    PCRE_INFO_OKPARTIAL
1125  .sp  .sp
1126  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
1127  fourth argument should point to an \fBint\fP variable. The  \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1128    \fBint\fP variable. From release 8.00, this always returns 1, because the
1129    restrictions that previously applied to partial matching have been lifted. The
1130  .\" HREF  .\" HREF
1131  \fBpcrepartial\fP  \fBpcrepartial\fP
1132  .\"  .\"
1133  documentation lists the restrictions that apply to patterns when partial  documentation gives details of partial matching.
 matching is used.  
1134  .sp  .sp
1135    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1136  .sp  .sp
1137  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
1138  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
1139  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
1140  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1141    they are the options that will be in force when matching starts. For example,
1142    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1143    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1144  .P  .P
1145  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
1146  alternatives begin with one of the following:  alternatives begin with one of the following:
# Line 971  variable. Line 1167  variable.
1167  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
1168  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
1169  \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
1170  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
1171    study data, zero is returned. The fourth argument should point to a
1172  \fBsize_t\fP variable.  \fBsize_t\fP variable.
1173  .  .
1174  .  .
# Line 1033  is different. (This seems a highly unlik Line 1230  is different. (This seems a highly unlik
1230  .P  .P
1231  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
1232  compiled pattern, which is passed in the \fIcode\fP argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1233  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
1234  \fIextra\fP argument. This function is the main matching facility of the  \fIextra\fP argument. This function is the main matching facility of the
1235  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
1236  also an alternative matching function, which is described  also an alternative matching function, which is described
# Line 1083  fields (not necessarily in this order): Line 1280  fields (not necessarily in this order):
1280    unsigned long int \fImatch_limit_recursion\fP;    unsigned long int \fImatch_limit_recursion\fP;
1281    void *\fIcallout_data\fP;    void *\fIcallout_data\fP;
1282    const unsigned char *\fItables\fP;    const unsigned char *\fItables\fP;
1283      unsigned char **\fImark\fP;
1284  .sp  .sp
1285  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
1286  are set. The flag bits are:  are set. The flag bits are:
# Line 1092  are set. The flag bits are: Line 1290  are set. The flag bits are:
1290    PCRE_EXTRA_MATCH_LIMIT_RECURSION    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1291    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1292    PCRE_EXTRA_TABLES    PCRE_EXTRA_TABLES
1293      PCRE_EXTRA_MARK
1294  .sp  .sp
1295  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
1296  \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 1101  the block by setting the other fields an Line 1300  the block by setting the other fields an
1300  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
1301  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,
1302  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
1303  classic example is the use of nested unlimited repeats.  classic example is a pattern that uses nested unlimited repeats.
1304  .P  .P
1305  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1306  (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 1134  with a \fBpcre_extra\fP block in which \ Line 1333  with a \fBpcre_extra\fP block in which \
1333  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
1334  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1335  .P  .P
1336  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,
1337  which is described in the  and is described in the
1338  .\" HREF  .\" HREF
1339  \fBpcrecallout\fP  \fBpcrecallout\fP
1340  .\"  .\"
# Line 1154  called. See the Line 1353  called. See the
1353  \fBpcreprecompile\fP  \fBpcreprecompile\fP
1354  .\"  .\"
1355  documentation for a discussion of saving compiled patterns for later use.  documentation for a discussion of saving compiled patterns for later use.
1356    .P
1357    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1358    be set to point to a \fBchar *\fP variable. If the pattern contains any
1359    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1360    a name to pass back, a pointer to the name string (zero terminated) is placed
1361    in the variable pointed to by the \fImark\fP field. The names are within the
1362    compiled pattern; if you wish to retain such a name you must copy it before
1363    freeing the memory of a compiled pattern. If there is no name to pass back, the
1364    variable pointed to by the \fImark\fP field set to NULL. For details of the
1365    backtracking control verbs, see the section entitled
1366    .\" HTML <a href="pcrepattern#backtrackcontrol">
1367    .\" </a>
1368    "Backtracking control"
1369    .\"
1370    in the
1371    .\" HREF
1372    \fBpcrepattern\fP
1373    .\"
1374    documentation.
1375  .  .
1376    .
1377    .\" HTML <a name="execoptions"></a>
1378  .SS "Option bits for \fBpcre_exec()\fP"  .SS "Option bits for \fBpcre_exec()\fP"
1379  .rs  .rs
1380  .sp  .sp
1381  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
1382  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,
1383  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1384    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1385    PCRE_PARTIAL_HARD.
1386  .sp  .sp
1387    PCRE_ANCHORED    PCRE_ANCHORED
1388  .sp  .sp
# Line 1169  matching position. If a pattern was comp Line 1391  matching position. If a pattern was comp
1391  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
1392  matching time.  matching time.
1393  .sp  .sp
1394      PCRE_BSR_ANYCRLF
1395      PCRE_BSR_UNICODE
1396    .sp
1397    These options (which are mutually exclusive) control what the \eR escape
1398    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1399    match any Unicode newline sequence. These options override the choice that was
1400    made or defaulted when the pattern was compiled.
1401    .sp
1402    PCRE_NEWLINE_CR    PCRE_NEWLINE_CR
1403    PCRE_NEWLINE_LF    PCRE_NEWLINE_LF
1404    PCRE_NEWLINE_CRLF    PCRE_NEWLINE_CRLF
# Line 1180  the pattern was compiled. For details, s Line 1410  the pattern was compiled. For details, s
1410  \fBpcre_compile()\fP above. During matching, the newline choice affects the  \fBpcre_compile()\fP above. During matching, the newline choice affects the
1411  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1412  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
1413  pattern. When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is  pattern.
1414  set, and a match attempt fails when the current position is at a CRLF sequence,  .P
1415  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
1416  words, to after the CRLF.  match attempt for an unanchored pattern fails when the current position is at a
1417    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1418    characters, the match position is advanced by two characters instead of one, in
1419    other words, to after the CRLF.
1420    .P
1421    The above rule is a compromise that makes the most common cases work as
1422    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1423    set), it does not match the string "\er\enA" because, after failing at the
1424    start, it skips both the CR and the LF before retrying. However, the pattern
1425    [\er\en]A does match that string, because it contains an explicit CR or LF
1426    reference, and so advances only by one character after the first failure.
1427    .P
1428    An explicit match for CR of LF is either a literal appearance of one of those
1429    characters, or one of the \er or \en escape sequences. Implicit matches such as
1430    [^X] do not count, nor does \es (which includes CR and LF in the characters
1431    that it matches).
1432    .P
1433    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1434    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1435  .sp  .sp
1436    PCRE_NOTBOL    PCRE_NOTBOL
1437  .sp  .sp
# Line 1209  match the empty string, the entire match Line 1457  match the empty string, the entire match
1457  .sp  .sp
1458    a?b?    a?b?
1459  .sp  .sp
1460  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
1461  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
1462  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".
1463  .P  .sp
1464  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1465  of a pattern match of the empty string within its \fBsplit()\fP function, and  .sp
1466  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
1467  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
1468  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the  can occur only if the pattern contains \eK.
1469  starting offset (see below) and trying an ordinary match again. There is some  .P
1470  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
1471    does make a special case of a pattern match of the empty string within its
1472    \fBsplit()\fP function, and when using the /g modifier. It is possible to
1473    emulate Perl's behaviour after matching a null string by first trying the match
1474    again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1475    if that fails, by advancing the starting offset (see below) and trying an
1476    ordinary match again. There is some code that demonstrates how to do this in
1477    the
1478    .\" HREF
1479    \fBpcredemo\fP
1480    .\"
1481    sample program. In the most general case, you have to check to see if the
1482    newline convention recognizes CRLF as a newline, and if so, and the current
1483    character is CR followed by LF, advance the starting offset by two characters
1484    instead of one.
1485    .sp
1486      PCRE_NO_START_OPTIMIZE
1487    .sp
1488    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1489    a match, in order to speed up the process. For example, if it is known that an
1490    unanchored match must start with a specific character, it searches the subject
1491    for that character, and fails immediately if it cannot find it, without
1492    actually running the main matching function. This means that a special item
1493    such as (*COMMIT) at the start of a pattern is not considered until after a
1494    suitable starting point for the match has been found. When callouts or (*MARK)
1495    items are in use, these "start-up" optimizations can cause them to be skipped
1496    if the pattern is never actually used. The start-up optimizations are in effect
1497    a pre-scan of the subject that takes place before the pattern is run.
1498    .P
1499    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1500    causing performance to suffer, but ensuring that in cases where the result is
1501    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1502    are considered at every possible starting position in the subject string. If
1503    PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1504    time.
1505    .P
1506    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1507    Consider the pattern
1508    .sp
1509      (*COMMIT)ABC
1510    .sp
1511    When this is compiled, PCRE records the fact that a match must start with the
1512    character "A". Suppose the subject string is "DEFABC". The start-up
1513    optimization scans along the subject, finds "A" and runs the first match
1514    attempt from there. The (*COMMIT) item means that the pattern must match the
1515    current starting position, which in this case, it does. However, if the same
1516    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1517    subject string does not happen. The first match attempt is run starting from
1518    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1519    the overall result is "no match". If the pattern is studied, more start-up
1520    optimizations may be used. For example, a minimum length for the subject may be
1521    recorded. Consider the pattern
1522    .sp
1523      (*MARK:A)(X|Y)
1524    .sp
1525    The minimum length for a match is one character. If the subject is "ABC", there
1526    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1527    If the pattern is studied, the final attempt does not take place, because PCRE
1528    knows that the subject is too short, and so the (*MARK) is never encountered.
1529    In this case, studying the pattern does not affect the overall match result,
1530    which is still "no match", but it does affect the auxiliary information that is
1531    returned.
1532  .sp  .sp
1533    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
1534  .sp  .sp
1535  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
1536  string is automatically checked when \fBpcre_exec()\fP is subsequently called.  string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1537  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
1538  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
1539  \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP  strings in the
1540  contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.  .\" HTML <a href="pcre.html#utf8strings">
1541    .\" </a>
1542    section on UTF-8 support
1543    .\"
1544    in the main
1545    .\" HREF
1546    \fBpcre\fP
1547    .\"
1548    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1549    the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1550    a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. If
1551    \fIstartoffset\fP contains a value that does not point to the start of a UTF-8
1552    character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1553    returned.
1554  .P  .P
1555  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
1556  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
1557  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
1558  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
1559  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
1560  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
1561  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
1562  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
1563  UTF-8 character, is undefined. Your program may crash.  undefined. Your program may crash.
1564  .sp  .sp
1565    PCRE_PARTIAL    PCRE_PARTIAL_HARD
1566  .sp    PCRE_PARTIAL_SOFT
1567  This option turns on the partial matching feature. If the subject string fails  .sp
1568  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
1569  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
1570  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
1571  characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of  not enough subject characters to complete the match. If this happens when
1572  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
1573  may appear in the pattern. These are discussed in the  testing any remaining alternatives. Only if no complete match can be found is
1574    PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1575    PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1576    but only if no complete match can be found.
1577    .P
1578    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1579    partial match is found, \fBpcre_exec()\fP immediately returns
1580    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1581    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1582    important that an alternative complete match.
1583    .P
1584    In both cases, the portion of the string that was inspected when the partial
1585    match was found is set as the first matching string. There is a more detailed
1586    discussion of partial and multi-segment matching, with examples, in the
1587  .\" HREF  .\" HREF
1588  \fBpcrepartial\fP  \fBpcrepartial\fP
1589  .\"  .\"
1590  documentation.  documentation.
1591  .  .
1592    .
1593  .SS "The string to be matched by \fBpcre_exec()\fP"  .SS "The string to be matched by \fBpcre_exec()\fP"
1594  .rs  .rs
1595  .sp  .sp
1596  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
1597  \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
1598  \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
1599  UTF-8 character. Unlike the pattern string, the subject may contain binary zero  subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1600  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,
1601  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
1602    point to the start of a UTF-8 character (or the end of the subject). Unlike the
1603    pattern string, the subject may contain binary zero bytes.
1604  .P  .P
1605  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
1606  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 1282  start of the subject, which is deemed to Line 1620  start of the subject, which is deemed to
1620  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
1621  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.
1622  .P  .P
1623    Finding all the matches in a subject is tricky when the pattern can match an
1624    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1625    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1626    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1627    and trying an ordinary match again. There is some code that demonstrates how to
1628    do this in the
1629    .\" HREF
1630    \fBpcredemo\fP
1631    .\"
1632    sample program. In the most general case, you have to check to see if the
1633    newline convention recognizes CRLF as a newline, and if so, and the current
1634    character is CR followed by LF, advance the starting offset by two characters
1635    instead of one.
1636    .P
1637  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
1638  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
1639  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.
1640  .  .
1641    .
1642  .SS "How \fBpcre_exec()\fP returns captured substrings"  .SS "How \fBpcre_exec()\fP returns captured substrings"
1643  .rs  .rs
1644  .sp  .sp
# Line 1296  pattern. Following the usage in Jeffrey Line 1649  pattern. Following the usage in Jeffrey
1649  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
1650  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1651  .P  .P
1652  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
1653  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
1654  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
1655  this argument is NOT the size of \fIovector\fP in bytes.  argument is NOT the size of \fIovector\fP in bytes.
1656  .P  .P
1657  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,
1658  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
1659  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1660  and is not available for passing back information. The length passed in  and is not available for passing back information. The number passed in
1661  \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
1662  rounded down.  rounded down.
1663  .P  .P
1664  When a match is successful, information about captured substrings is returned  When a match is successful, information about captured substrings is returned
1665  in pairs of integers, starting at the beginning of \fIovector\fP, and  in pairs of integers, starting at the beginning of \fIovector\fP, and
1666  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
1667  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
1668  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
1669  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
1670  subject string matched by the entire pattern. The next pair is used for the  mode. They are not character counts.
1671  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP  .P
1672  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
1673  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
1674  capturing subpatterns, the return value from a successful match is 1,  used for the first capturing subpattern, and so on. The value returned by
1675  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.
1676    For example, if two substrings have been captured, the returned value is 3. If
1677    there are no capturing subpatterns, the return value from a successful match is
1678    1, indicating that just the first pair of offsets has been set.
1679  .P  .P
1680  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
1681  string that it matched that is returned.  string that it matched that is returned.
1682  .P  .P
1683  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
1684  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
1685  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,
1686  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
1687  \fIovecsize\fP as zero. However, if the pattern contains back references and  \fIovecsize\fP as zero. However, if the pattern contains back references and
1688  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
1689  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
1690  advisable to supply an \fIovector\fP.  advisable to supply an \fIovector\fP.
1691  .P  .P
1692  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
1693  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1694  \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
1695  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 1349  Offset values that correspond to unused Line 1705  Offset values that correspond to unused
1705  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
1706  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
1707  return from the function is 2, because the highest used capturing subpattern  return from the function is 2, because the highest used capturing subpattern
1708  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
1709  capturing subpatterns if you wish (assuming the vector is large enough, of  (assuming the vector is large enough, of course) are set to -1.
1710  course).  .P
1711    \fBNote\fP: Elements of \fIovector\fP that do not correspond to capturing
1712    parentheses in the pattern are never changed. That is, if a pattern contains
1713    \fIn\fP capturing parentheses, no more than \fIovector[0]\fP to
1714    \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other elements retain
1715    whatever values they previously had.
1716  .P  .P
1717  Some convenience functions are provided for extracting the captured substrings  Some convenience functions are provided for extracting the captured substrings
1718  as separate strings. These are described below.  as separate strings. These are described below.
# Line 1397  If a pattern contains back references, b Line 1758  If a pattern contains back references, b
1758  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
1759  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
1760  automatically freed at the end of matching.  automatically freed at the end of matching.
1761    .P
1762    This error is also given if \fBpcre_stack_malloc()\fP fails in
1763    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1764    \fB--disable-stack-for-recursion\fP.
1765  .sp  .sp
1766    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1767  .sp  .sp
# Line 1422  documentation for details. Line 1787  documentation for details.
1787    PCRE_ERROR_BADUTF8        (-10)    PCRE_ERROR_BADUTF8        (-10)
1788  .sp  .sp
1789  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.
1790    However, if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8
1791    character at the end of the subject, PCRE_ERROR_SHORTUTF8 is used instead.
1792  .sp  .sp
1793    PCRE_ERROR_BADUTF8_OFFSET (-11)    PCRE_ERROR_BADUTF8_OFFSET (-11)
1794  .sp  .sp
1795  The UTF-8 byte sequence that was passed as a subject was valid, but the value  The UTF-8 byte sequence that was passed as a subject was valid, but the value
1796  of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.  of \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
1797    end of the subject.
1798  .sp  .sp
1799    PCRE_ERROR_PARTIAL        (-12)    PCRE_ERROR_PARTIAL        (-12)
1800  .sp  .sp
# Line 1438  documentation for details of partial mat Line 1806  documentation for details of partial mat
1806  .sp  .sp
1807    PCRE_ERROR_BADPARTIAL     (-13)    PCRE_ERROR_BADPARTIAL     (-13)
1808  .sp  .sp
1809  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
1810  are not supported for partial matching. See the  option was used with a compiled pattern containing items that were not
1811  .\" HREF  supported for partial matching. From release 8.00 onwards, there are no
1812  \fBpcrepartial\fP  restrictions on partial matching.
 .\"  
 documentation for details of partial matching.  
1813  .sp  .sp
1814    PCRE_ERROR_INTERNAL       (-14)    PCRE_ERROR_INTERNAL       (-14)
1815  .sp  .sp
# Line 1460  The internal recursion limit, as specifi Line 1826  The internal recursion limit, as specifi
1826  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
1827  description above.  description above.
1828  .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  
1829    PCRE_ERROR_BADNEWLINE     (-23)    PCRE_ERROR_BADNEWLINE     (-23)
1830  .sp  .sp
1831  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1832    .sp
1833      PCRE_ERROR_BADOFFSET      (-24)
1834    .sp
1835    The value of \fIstartoffset\fP was negative or greater than the length of the
1836    subject, that is, the value in \fIlength\fP.
1837    .sp
1838      PCRE_ERROR_SHORTUTF8      (-25)
1839    .sp
1840    The subject string ended with an incomplete (truncated) UTF-8 character, and
1841    the PCRE_PARTIAL_HARD option was set. Without this option, PCRE_ERROR_BADUTF8
1842    is returned in this situation.
1843  .P  .P
1844  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.
1845  .  .
1846  .  .
1847  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
# Line 1621  These functions call \fBpcre_get_stringn Line 1990  These functions call \fBpcre_get_stringn
1990  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1991  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,
1992  the behaviour may not be what you want (see the next section).  the behaviour may not be what you want (see the next section).
1993  .  .P
1994    \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1995    subpatterns with the same number, as described in the
1996    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1997    .\" </a>
1998    section on duplicate subpattern numbers
1999    .\"
2000    in the
2001    .\" HREF
2002    \fBpcrepattern\fP
2003    .\"
2004    page, you cannot use names to distinguish the different subpatterns, because
2005    names are not included in the compiled code. The matching process uses only
2006    numbers. For this reason, the use of different names for subpatterns of the
2007    same number causes an error at compile time.
2008  .  .
2009  .SH "DUPLICATE SUBPATTERN NAMES"  .SH "DUPLICATE SUBPATTERN NAMES"
2010  .rs  .rs
# Line 1631  the behaviour may not be what you want ( Line 2014  the behaviour may not be what you want (
2014  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2015  .PP  .PP
2016  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
2017  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
2018  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
2019  example is shown in the  such subpatterns are named, they are required to use the same names.)
2020    .P
2021    Normally, patterns with duplicate names are such that in any one match, only
2022    one of the named subpatterns participates. An example is shown in the
2023  .\" HREF  .\" HREF
2024  \fBpcrepattern\fP  \fBpcrepattern\fP
2025  .\"  .\"
2026  documentation. When duplicates are present, \fBpcre_copy_named_substring()\fP  documentation.
2027  and \fBpcre_get_named_substring()\fP return the first substring corresponding  .P
2028  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
2029  The \fBpcre_get_stringnumber()\fP function returns one of the numbers that are  \fBpcre_get_named_substring()\fP return the first substring corresponding to
2030  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
2031  .sp  returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2032    returns one of the numbers that are associated with the name, but it is not
2033    defined which it is.
2034    .P
2035  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,
2036  you must use the \fBpcre_get_stringtable_entries()\fP function. The first  you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2037  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 1694  a compiled pattern, using a matching alg Line 2083  a compiled pattern, using a matching alg
2083  just once, and does not backtrack. This has different characteristics to the  just once, and does not backtrack. This has different characteristics to the
2084  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
2085  patterns are not supported. Nevertheless, there are times when this kind of  patterns are not supported. Nevertheless, there are times when this kind of
2086  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
2087  the  list of features that \fBpcre_dfa_exec()\fP does not support, see the
2088  .\" HREF  .\" HREF
2089  \fBpcrematching\fP  \fBpcrematching\fP
2090  .\"  .\"
# Line 1734  Here is an example of a simple call to \ Line 2123  Here is an example of a simple call to \
2123  .sp  .sp
2124  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
2125  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,
2126  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2127  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,
2128  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.
2129  .sp  All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2130    PCRE_PARTIAL  so their description is not repeated here.
2131  .sp  .sp
2132  This has the same general effect as it does for \fBpcre_exec()\fP, but the    PCRE_PARTIAL_HARD
2133  details are slightly different. When PCRE_PARTIAL is set for    PCRE_PARTIAL_SOFT
2134  \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into  .sp
2135  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
2136  complete matches, but there is still at least one matching possibility. The  details are slightly different. When PCRE_PARTIAL_HARD is set for
2137  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
2138  matching string.  is reached and there is still at least one matching possibility that requires
2139    additional characters. This happens even if some complete matches have also
2140    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2141    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2142    there have been no complete matches, but there is still at least one matching
2143    possibility. The portion of the string that was inspected when the longest
2144    partial match was found is set as the first matching string in both cases.
2145    There is a more detailed discussion of partial and multi-segment matching, with
2146    examples, in the
2147    .\" HREF
2148    \fBpcrepartial\fP
2149    .\"
2150    documentation.
2151  .sp  .sp
2152    PCRE_DFA_SHORTEST    PCRE_DFA_SHORTEST
2153  .sp  .sp
# Line 1757  matching point in the subject string. Line 2158  matching point in the subject string.
2158  .sp  .sp
2159    PCRE_DFA_RESTART    PCRE_DFA_RESTART
2160  .sp  .sp
2161  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
2162  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
2163  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
2164  option requests this action; when it is set, the \fIworkspace\fP and  \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2165  \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
2166  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  
2167  .\" HREF  .\" HREF
2168  \fBpcrepartial\fP  \fBpcrepartial\fP
2169  .\"  .\"
# Line 1867  Cambridge CB2 3QH, England. Line 2267  Cambridge CB2 3QH, England.
2267  .rs  .rs
2268  .sp  .sp
2269  .nf  .nf
2270  Last updated: 04 June 2007  Last updated: 21 November 2010
2271  Copyright (c) 1997-2007 University of Cambridge.  Copyright (c) 1997-2010 University of Cambridge.
2272  .fi  .fi

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