/[pcre]/code/trunk/doc/pcre.txt

Diff of /code/trunk/doc/pcre.txt

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-revision 69 by nigel,
Sat Feb 24 21:40:18 2007 UTC
+revision 345 by ph10,
Mon Apr 28 15:10:02 2008 UTC
 Line 1
+ -----------------------------------------------------------------------------
  This file contains a concatenation of the PCRE man pages, converted to plain
  text format for ease of searching with a text editor, or for use on systems
  that do not have a man page processor. The small individual files that give
-Line 5 
 synopses of each function in the library
+Line 6 
 synopses of each function in the library
  separate text files for the pcregrep and pcretest commands.
  -----------------------------------------------------------------------------
+ PCRE(3)                                                                PCRE(3)
  NAME
-      PCRE - Perl-compatible regular expressions
+        PCRE - Perl-compatible regular expressions
- DESCRIPTION
+ INTRODUCTION
-      The PCRE library is a set of functions that implement  regu-
+        The  PCRE  library is a set of functions that implement regular expres-
-      lar  expression  pattern  matching using the same syntax and
+        sion pattern matching using the same syntax and semantics as Perl, with
-      semantics as Perl, with just a few differences. The  current
+        just  a  few  differences. Certain features that appeared in Python and
-      implementation  of  PCRE  (release 4.x) corresponds approxi-
+        PCRE before they appeared in Perl are also available using  the  Python
-      mately with Perl 5.8, including support  for  UTF-8  encoded
+        syntax.  There is also some support for certain .NET and Oniguruma syn-
-      strings.    However,  this  support  has  to  be  explicitly
+        tax items, and there is an option for  requesting  some  minor  changes
-      enabled; it is not the default.
+        that give better JavaScript compatibility.
-      PCRE is written in C and released as a C library. However, a
+        The  current  implementation of PCRE (release 7.x) corresponds approxi-
-      number  of  people  have  written wrappers and interfaces of
+        mately with Perl 5.10, including support for UTF-8 encoded strings  and
-      various kinds. A C++ class is included  in  these  contribu-
+        Unicode general category properties. However, UTF-8 and Unicode support
-      tions,  which  can  be found in the Contrib directory at the
+        has to be explicitly enabled; it is not the default. The Unicode tables
-      primary FTP site, which is:
+        correspond to Unicode release 5.0.0.
-      ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
+        In  addition to the Perl-compatible matching function, PCRE contains an
+        alternative matching function that matches the same  compiled  patterns
-      Details of exactly which Perl  regular  expression  features
+        in  a different way. In certain circumstances, the alternative function
-      are  and  are  not  supported  by PCRE are given in separate
+        has some advantages. For a discussion of the two  matching  algorithms,
-      documents. See the pcrepattern and pcrecompat pages.
+        see the pcrematching page.
-      Some features of PCRE can be included, excluded, or  changed
+        PCRE  is  written  in C and released as a C library. A number of people
-      when  the library is built. The pcre_config() function makes
+        have written wrappers and interfaces of various kinds.  In  particular,
-      it possible for a client  to  discover  which  features  are
+        Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
-      available.  Documentation  about  building  PCRE for various
+        included as part of the PCRE distribution. The pcrecpp page has details
-      operating systems can be found in the  README  file  in  the
+        of  this  interface.  Other  people's contributions can be found in the
-      source distribution.
+        Contrib directory at the primary FTP site, which is:
+        ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
+        Details of exactly which Perl regular expression features are  and  are
+        not supported by PCRE are given in separate documents. See the pcrepat-
+        tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
+        page.
+        Some  features  of  PCRE can be included, excluded, or changed when the
+        library is built. The pcre_config() function makes it  possible  for  a
+        client  to  discover  which  features are available. The features them-
+        selves are described in the pcrebuild page. Documentation about  build-
+        ing  PCRE for various operating systems can be found in the README file
+        in the source distribution.
+        The library contains a number of undocumented  internal  functions  and
+        data  tables  that  are  used by more than one of the exported external
+        functions, but which are not intended  for  use  by  external  callers.
+        Their  names  all begin with "_pcre_", which hopefully will not provoke
+        any name clashes. In some environments, it is possible to control which
+        external  symbols  are  exported when a shared library is built, and in
+        these cases the undocumented symbols are not exported.
  USER DOCUMENTATION
-      The user documentation for PCRE has been  split  up  into  a
+        The user documentation for PCRE comprises a number  of  different  sec-
-      number  of  different sections. In the "man" format, each of
+        tions.  In the "man" format, each of these is a separate "man page". In
-      these is a separate "man page". In the HTML format, each  is
+        the HTML format, each is a separate page, linked from the  index  page.
-      a  separate  page,  linked from the index page. In the plain
+        In  the  plain text format, all the sections are concatenated, for ease
-      text format, all the sections are concatenated, for ease  of
+        of searching. The sections are as follows:
-      searching. The sections are as follows:
+          pcre              this document
-        pcre              this document
+          pcre-config       show PCRE installation configuration information
-        pcreapi           details of PCRE's native API
+          pcreapi           details of PCRE's native C API
-        pcrebuild         options for building PCRE
+          pcrebuild         options for building PCRE
-        pcrecallout       details of the callout feature
+          pcrecallout       details of the callout feature
-        pcrecompat        discussion of Perl compatibility
+          pcrecompat        discussion of Perl compatibility
-        pcregrep          description of the pcregrep command
+          pcrecpp           details of the C++ wrapper
-        pcrepattern       syntax and semantics of supported
+          pcregrep          description of the pcregrep command
-                            regular expressions
+          pcrematching      discussion of the two matching algorithms
-        pcreperform       discussion of performance issues
+          pcrepartial       details of the partial matching facility
-        pcreposix         the POSIX-compatible API
+          pcrepattern       syntax and semantics of supported
-        pcresample        discussion of the sample program
+                              regular expressions
-        pcretest          the pcretest testing command
+          pcresyntax        quick syntax reference
+          pcreperform       discussion of performance issues
-      In addition, in the "man" and HTML formats, there is a short
+          pcreposix         the POSIX-compatible C API
-      page  for  each  library function, listing its arguments and
+          pcreprecompile    details of saving and re-using precompiled patterns
-      results.
+          pcresample        discussion of the sample program
+          pcrestack         discussion of stack usage
+          pcretest          description of the pcretest testing command
+        In  addition,  in the "man" and HTML formats, there is a short page for
+        each C library function, listing its arguments and results.
  LIMITATIONS
-      There are some size limitations in PCRE but it is hoped that
+        There are some size limitations in PCRE but it is hoped that they  will
-      they will never in practice be relevant.
+        never in practice be relevant.
-      The maximum length of a  compiled  pattern  is  65539  (sic)
+        The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE
-      bytes  if PCRE is compiled with the default internal linkage
+        is compiled with the default internal linkage size of 2. If you want to
-      size of 2. If you want to process regular  expressions  that
+        process  regular  expressions  that are truly enormous, you can compile
-      are  truly  enormous,  you can compile PCRE with an internal
+        PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
-      linkage size of 3 or 4 (see the README file  in  the  source
+        the  source  distribution and the pcrebuild documentation for details).
-      distribution  and  the pcrebuild documentation for details).
+        In these cases the limit is substantially larger.  However,  the  speed
-      If these cases the limit is substantially larger.   However,
+        of execution is slower.
-      the speed of execution will be slower.
+        All values in repeating quantifiers must be less than 65536.
-      All values in repeating quantifiers must be less than 65536.
-      The maximum number of capturing subpatterns is 65535.
+        There is no limit to the number of parenthesized subpatterns, but there
+        can be no more than 65535 capturing subpatterns.
-      There is no limit to the  number  of  non-capturing  subpat-
-      terns,  but  the  maximum  depth  of nesting of all kinds of
+        The maximum length of name for a named subpattern is 32 characters, and
-      parenthesized subpattern, including  capturing  subpatterns,
+        the maximum number of named subpatterns is 10000.
-      assertions, and other types of subpattern, is 200.
+        The  maximum  length of a subject string is the largest positive number
-      The maximum length of a subject string is the largest  posi-
+        that an integer variable can hold. However, when using the  traditional
-      tive number that an integer variable can hold. However, PCRE
+        matching function, PCRE uses recursion to handle subpatterns and indef-
-      uses recursion to handle subpatterns and indefinite  repeti-
+        inite repetition.  This means that the available stack space may  limit
-      tion.  This  means  that the available stack space may limit
+        the size of a subject string that can be processed by certain patterns.
-      the size of a subject string that can be processed  by  cer-
+        For a discussion of stack issues, see the pcrestack documentation.
-      tain patterns.
+ UTF-8 AND UNICODE PROPERTY SUPPORT
+        From release 3.3, PCRE has  had  some  support  for  character  strings
+        encoded  in the UTF-8 format. For release 4.0 this was greatly extended
+        to cover most common requirements, and in release 5.0  additional  sup-
+        port for Unicode general category properties was added.
+        In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
+        support in the code, and, in addition,  you  must  call  pcre_compile()
+        with  the PCRE_UTF8 option flag. When you do this, both the pattern and
+        any subject strings that are matched against it are  treated  as  UTF-8
+        strings instead of just strings of bytes.
+        If  you compile PCRE with UTF-8 support, but do not use it at run time,
+        the library will be a bit bigger, but the additional run time  overhead
+        is limited to testing the PCRE_UTF8 flag occasionally, so should not be
+        very big.
+        If PCRE is built with Unicode character property support (which implies
+        UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
+        ported.  The available properties that can be tested are limited to the
+        general  category  properties such as Lu for an upper case letter or Nd
+        for a decimal number, the Unicode script names such as Arabic  or  Han,
+        and  the  derived  properties  Any  and L&. A full list is given in the
+        pcrepattern documentation. Only the short names for properties are sup-
+        ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-
+        ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
+        optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
+        does not support this.
+    Validity of UTF-8 strings
+        When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
+        subjects are (by default) checked for validity on entry to the relevant
+        functions. From release 7.3 of PCRE, the check is according  the  rules
+        of  RFC  3629, which are themselves derived from the Unicode specifica-
+        tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
+        allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
+        check allows only values in the range U+0 to U+10FFFF, excluding U+D800
+        to U+DFFF.
+        The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
+        which the Unicode Standard says this: "The Low Surrogate Area does  not
+        contain  any  character  assignments,  consequently  no  character code
+        charts or namelists are provided for this area. Surrogates are reserved
+        for  use  with  UTF-16 and then must be used in pairs." The code points
+        that are encoded by UTF-16 pairs  are  available  as  independent  code
+        points  in  the  UTF-8  encoding.  (In other words, the whole surrogate
+        thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
+        If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return
+        (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
+        that your strings are valid, and therefore want to skip these checks in
+        order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
+        compile time or at run time, PCRE assumes that the pattern  or  subject
+        it  is  given  (respectively)  contains only valid UTF-8 codes. In this
+        case, it does not diagnose an invalid UTF-8 string.
+        If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,
+        what  happens  depends on why the string is invalid. If the string con-
+        forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
+        string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,
+        apart from the initial validity test, PCRE (when in UTF-8 mode) handles
+        strings  according  to  the more liberal rules of RFC 2279. However, if
+        the string does not even conform to RFC 2279, the result is  undefined.
+        Your program may crash.
+        If  you  want  to  process  strings  of  values  in the full range 0 to
+x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can
+        set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
+        this situation, you will have to apply your own validity check.
+    General comments about UTF-8 mode
+. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
+        two-byte UTF-8 character if the value is greater than 127.
+.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8
+        characters for values greater than \177.
+. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
+        vidual bytes, for example: \x{100}{3}.
+.  The dot metacharacter matches one UTF-8 character instead of a sin-
+        gle byte.
+. The escape sequence \C can be used to match a single byte  in  UTF-8
+        mode,  but  its  use can lead to some strange effects. This facility is
+        not available in the alternative matching function, pcre_dfa_exec().
+. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly
+        test  characters of any code value, but the characters that PCRE recog-
+        nizes as digits, spaces, or word characters  remain  the  same  set  as
+        before, all with values less than 256. This remains true even when PCRE
+        includes Unicode property support, because to do otherwise  would  slow
+        down  PCRE in many common cases. If you really want to test for a wider
+        sense of, say, "digit", you must use Unicode  property  tests  such  as
+        \p{Nd}.
+.  Similarly,  characters that match the POSIX named character classes
+        are all low-valued characters.
+. However, the Perl 5.10 horizontal and vertical  whitespace  matching
+        escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
+        acters.
+. Case-insensitive matching applies only to  characters  whose  values
+        are  less than 128, unless PCRE is built with Unicode property support.
+        Even when Unicode property support is available, PCRE  still  uses  its
+        own  character  tables when checking the case of low-valued characters,
+        so as not to degrade performance.  The Unicode property information  is
+        used only for characters with higher values. Even when Unicode property
+        support is available, PCRE supports case-insensitive matching only when
+        there  is  a  one-to-one  mapping between a letter's cases. There are a
+        small number of many-to-one mappings in Unicode;  these  are  not  sup-
+        ported by PCRE.
- UTF-8 SUPPORT
+ AUTHOR
-      Starting at release 3.3, PCRE has had some support for char-
+        Philip Hazel
-      acter  strings  encoded in the UTF-8 format. For release 4.0
+        University Computing Service
-      this has been greatly extended to cover most common require-
+        Cambridge CB2 3QH, England.
-      ments.
-      In order process UTF-8  strings,  you  must  build  PCRE  to
-      include  UTF-8  support  in  the code, and, in addition, you
-      must call pcre_compile() with  the  PCRE_UTF8  option  flag.
-      When  you  do this, both the pattern and any subject strings
-      that are matched against it are  treated  as  UTF-8  strings
-      instead of just strings of bytes.
-      If you compile PCRE with UTF-8 support, but do not use it at
-      run  time,  the  library will be a bit bigger, but the addi-
-      tional run time overhead is limited to testing the PCRE_UTF8
-      flag in several places, so should not be very large.
-      The following comments apply when PCRE is running  in  UTF-8
-      mode:
-. PCRE assumes that the strings it is given  contain  valid
-      UTF-8  codes. It does not diagnose invalid UTF-8 strings. If
-      you pass invalid UTF-8 strings  to  PCRE,  the  results  are
-      undefined.
-. In a pattern, the escape sequence \x{...}, where the con-
-      tents  of  the  braces is a string of hexadecimal digits, is
-      interpreted as a UTF-8 character whose code  number  is  the
-      given  hexadecimal  number, for example: \x{1234}. If a non-
-      hexadecimal digit appears between the braces,  the  item  is
-      not  recognized.  This escape sequence can be used either as
-      a literal, or within a character class.
-. The original hexadecimal escape sequence, \xhh, matches a
-      two-byte UTF-8 character if the value is greater than 127.
-. Repeat quantifiers apply to  complete  UTF-8  characters,
-      not to individual bytes, for example: \x{100}{3}.
-. The dot metacharacter matches one UTF-8 character instead
-      of a single byte.
-. The escape sequence \C can be used to match a single byte
-      in UTF-8 mode, but its use can lead to some strange effects.
-. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W
-      correctly test characters of any code value, but the charac-
-      ters that PCRE recognizes as digits, spaces, or word charac-
-      ters  remain  the  same  set as before, all with values less
-      than 256.
-. Case-insensitive  matching  applies  only  to  characters
-      whose  values  are  less than 256. PCRE does not support the
-      notion of "case" for higher-valued characters.
-. PCRE does not support the use of Unicode tables and  pro-
+        Putting  an actual email address here seems to have been a spam magnet,
-      perties or the Perl escapes \p, \P, and \X.
+        so I've taken it away. If you want to email me, use  my  two  initials,
+        followed by the two digits 10, at the domain cam.ac.uk.
- AUTHOR
+ REVISION
-      Philip Hazel <ph10@cam.ac.uk>
+        Last updated: 12 April 2008
-      University Computing Service,
+        Copyright (c) 1997-2008 University of Cambridge.
-      Cambridge CB2 3QG, England.
+ ------------------------------------------------------------------------------
-      Phone: +44 1223 334714
+ PCREBUILD(3)                                                      PCREBUILD(3)
- Last updated: 04 February 2003
- Copyright (c) 1997-2003 University of Cambridge.
- -----------------------------------------------------------------------------
  NAME
-      PCRE - Perl-compatible regular expressions
+        PCRE - Perl-compatible regular expressions
  PCRE BUILD-TIME OPTIONS
-      This document describes the optional features of  PCRE  that
+        This  document  describes  the  optional  features  of PCRE that can be
-      can  be  selected when the library is compiled. They are all
+        selected when the library is compiled. It assumes use of the  configure
-      selected, or deselected, by providing options to the config-
+        script,  where the optional features are selected or deselected by pro-
-      ure  script  which  is run before the make command. The com-
+        viding options to configure before running the make  command.  However,
-      plete list of options  for  configure  (which  includes  the
+        the  same  options  can be selected in both Unix-like and non-Unix-like
-      standard  ones  such  as  the  selection of the installation
+        environments using the GUI facility of  CMakeSetup  if  you  are  using
-      directory) can be obtained by running
+        CMake instead of configure to build PCRE.
-        ./configure --help
+        The complete list of options for configure (which includes the standard
+        ones such as the  selection  of  the  installation  directory)  can  be
-      The following sections describe certain options whose  names
+        obtained by running
-      begin  with  --enable  or  --disable. These settings specify
-      changes to the defaults for the configure  command.  Because
+          ./configure --help
-      of  the  way  that  configure  works, --enable and --disable
-      always come in pairs, so  the  complementary  option  always
+        The  following  sections  include  descriptions  of options whose names
-      exists  as  well, but as it specifies the default, it is not
+        begin with --enable or --disable. These settings specify changes to the
-      described.
+        defaults  for  the configure command. Because of the way that configure
+        works, --enable and --disable always come in pairs, so  the  complemen-
+        tary  option always exists as well, but as it specifies the default, it
+        is not described.
+ C++ SUPPORT
+        By default, the configure script will search for a C++ compiler and C++
+        header files. If it finds them, it automatically builds the C++ wrapper
+        library for PCRE. You can disable this by adding
+          --disable-cpp
+        to the configure command.
  UTF-8 SUPPORT
-      To build PCRE with support for UTF-8 character strings, add
+        To build PCRE with support for UTF-8 character strings, add
+          --enable-utf8
+        to the configure command. Of itself, this  does  not  make  PCRE  treat
+        strings  as UTF-8. As well as compiling PCRE with this option, you also
+        have have to set the PCRE_UTF8 option when you call the  pcre_compile()
+        function.
+ UNICODE CHARACTER PROPERTY SUPPORT
-        --enable-utf8
+        UTF-8  support allows PCRE to process character values greater than 255
+        in the strings that it handles. On its own, however, it does  not  pro-
+        vide any facilities for accessing the properties of such characters. If
+        you want to be able to use the pattern escapes \P, \p,  and  \X,  which
+        refer to Unicode character properties, you must add
-      to the configure command. Of itself, this does not make PCRE
+          --enable-unicode-properties
-      treat  strings as UTF-8. As well as compiling PCRE with this
-      option, you also have have to set the PCRE_UTF8 option  when
+        to  the configure command. This implies UTF-8 support, even if you have
-      you call the pcre_compile() function.
+        not explicitly requested it.
+        Including Unicode property support adds around 30K  of  tables  to  the
+        PCRE  library.  Only  the general category properties such as Lu and Nd
+        are supported. Details are given in the pcrepattern documentation.
  CODE VALUE OF NEWLINE
-      By default, PCRE treats character 10 (linefeed) as the  new-
+        By default, PCRE interprets character 10 (linefeed, LF)  as  indicating
-      line  character.  This  is  the  normal newline character on
+        the  end  of  a line. This is the normal newline character on Unix-like
-      Unix-like systems. You can compile PCRE to use character  13
+        systems. You can compile PCRE to use character 13 (carriage return, CR)
-      (carriage return) instead by adding
+        instead, by adding
-        --enable-newline-is-cr
+          --enable-newline-is-cr
-      to the configure command. For completeness there is  also  a
+        to  the  configure  command.  There  is  also  a --enable-newline-is-lf
-      --enable-newline-is-lf  option,  which  explicitly specifies
+        option, which explicitly specifies linefeed as the newline character.
-      linefeed as the newline character.
+        Alternatively, you can specify that line endings are to be indicated by
+        the two character sequence CRLF. If you want this, add
+          --enable-newline-is-crlf
+        to the configure command. There is a fourth option, specified by
+          --enable-newline-is-anycrlf
+        which  causes  PCRE  to recognize any of the three sequences CR, LF, or
+        CRLF as indicating a line ending. Finally, a fifth option, specified by
+          --enable-newline-is-any
+        causes PCRE to recognize any Unicode newline sequence.
+        Whatever  line  ending convention is selected when PCRE is built can be
+        overridden when the library functions are called. At build time  it  is
+        conventional to use the standard for your operating system.
+ WHAT \R MATCHES
+        By  default,  the  sequence \R in a pattern matches any Unicode newline
+        sequence, whatever has been selected as the line  ending  sequence.  If
+        you specify
+          --enable-bsr-anycrlf
+        the  default  is changed so that \R matches only CR, LF, or CRLF. What-
+        ever is selected when PCRE is built can be overridden when the  library
+        functions are called.
  BUILDING SHARED AND STATIC LIBRARIES
-      The PCRE building process uses libtool to build both  shared
+        The  PCRE building process uses libtool to build both shared and static
-      and  static  Unix libraries by default. You can suppress one
+        Unix libraries by default. You can suppress one of these by adding  one
-      of these by adding one of
+        of
-        --disable-shared
+          --disable-shared
-        --disable-static
+          --disable-static
-      to the configure command, as required.
+        to the configure command, as required.
  POSIX MALLOC USAGE
-      When PCRE is called through the  POSIX  interface  (see  the
+        When PCRE is called through the POSIX interface (see the pcreposix doc-
-      pcreposix  documentation),  additional  working  storage  is
+        umentation), additional working storage is  required  for  holding  the
-      required for holding the pointers  to  capturing  substrings
+        pointers  to capturing substrings, because PCRE requires three integers
-      because  PCRE requires three integers per substring, whereas
+        per substring, whereas the POSIX interface provides only  two.  If  the
-      the POSIX interface provides only  two.  If  the  number  of
+        number of expected substrings is small, the wrapper function uses space
-      expected  substrings  is  small,  the  wrapper function uses
+        on the stack, because this is faster than using malloc() for each call.
-      space on the stack, because this is faster than  using  mal-
+        The default threshold above which the stack is no longer used is 10; it
-      loc()  for  each call. The default threshold above which the
+        can be changed by adding a setting such as
-      stack is no longer used is 10; it can be changed by adding a
-      setting such as
+          --with-posix-malloc-threshold=20
+        to the configure command.
-        --with-posix-malloc-threshold=20
+ HANDLING VERY LARGE PATTERNS
-      to the configure command.
+        Within a compiled pattern, offset values are used  to  point  from  one
+        part  to another (for example, from an opening parenthesis to an alter-
+        nation metacharacter). By default, two-byte values are used  for  these
+        offsets,  leading  to  a  maximum size for a compiled pattern of around
+K. This is sufficient to handle all but the most  gigantic  patterns.
+        Nevertheless,  some  people do want to process enormous patterns, so it
+        is possible to compile PCRE to use three-byte or four-byte  offsets  by
+        adding a setting such as
+          --with-link-size=3
+        to  the  configure  command.  The value given must be 2, 3, or 4. Using
+        longer offsets slows down the operation of PCRE because it has to  load
+        additional bytes when handling them.
+ AVOIDING EXCESSIVE STACK USAGE
+        When matching with the pcre_exec() function, PCRE implements backtrack-
+        ing by making recursive calls to an internal function  called  match().
+        In  environments  where  the size of the stack is limited, this can se-
+        verely limit PCRE's operation. (The Unix environment does  not  usually
+        suffer from this problem, but it may sometimes be necessary to increase
+        the maximum stack size.  There is a discussion in the  pcrestack  docu-
+        mentation.)  An alternative approach to recursion that uses memory from
+        the heap to remember data, instead of using recursive  function  calls,
+        has  been  implemented to work round the problem of limited stack size.
+        If you want to build a version of PCRE that works this way, add
+          --disable-stack-for-recursion
+        to the configure command. With this configuration, PCRE  will  use  the
+        pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
+        ment functions. By default these point to malloc() and free(), but  you
+        can replace the pointers so that your own functions are used.
+        Separate  functions  are  provided  rather  than  using pcre_malloc and
+        pcre_free because the  usage  is  very  predictable:  the  block  sizes
+        requested  are  always  the  same,  and  the blocks are always freed in
+        reverse order. A calling program might be able to  implement  optimized
+        functions  that  perform  better  than  malloc()  and free(). PCRE runs
+        noticeably more slowly when built in this way. This option affects only
+        the   pcre_exec()   function;   it   is   not   relevant  for  the  the
+        pcre_dfa_exec() function.
  LIMITING PCRE RESOURCE USAGE
-      Internally, PCRE has a  function  called  match()  which  it
+        Internally, PCRE has a function called match(), which it calls  repeat-
-      calls  repeatedly  (possibly  recursively) when performing a
+        edly   (sometimes   recursively)  when  matching  a  pattern  with  the
-      matching operation. By limiting the  number  of  times  this
+        pcre_exec() function. By controlling the maximum number of  times  this
-      function  may  be  called,  a  limit  can  be  placed on the
+        function  may be called during a single matching operation, a limit can
-      resources used by a single call to  pcre_exec().  The  limit
+        be placed on the resources used by a single call  to  pcre_exec().  The
-      can  be  changed  at  run  time, as described in the pcreapi
+        limit  can be changed at run time, as described in the pcreapi documen-
-      documentation. The default is 10 million, but  this  can  be
+        tation. The default is 10 million, but this can be changed by adding  a
-      changed by adding a setting such as
+        setting such as
-        --with-match-limit=500000
+          --with-match-limit=500000
-      to the configure command.
+        to   the   configure  command.  This  setting  has  no  effect  on  the
+        pcre_dfa_exec() matching function.
+        In some environments it is desirable to limit the  depth  of  recursive
+        calls of match() more strictly than the total number of calls, in order
+        to restrict the maximum amount of stack (or heap,  if  --disable-stack-
+        for-recursion is specified) that is used. A second limit controls this;
+        it defaults to the value that  is  set  for  --with-match-limit,  which
+        imposes  no  additional constraints. However, you can set a lower limit
+        by adding, for example,
- HANDLING VERY LARGE PATTERNS
+          --with-match-limit-recursion=10000
-      Within a compiled pattern, offset values are used  to  point
+        to the configure command. This value can  also  be  overridden  at  run
-      from  one  part  to  another  (for  example, from an opening
+        time.
-      parenthesis to an  alternation  metacharacter).  By  default
-      two-byte  values  are  used  for these offsets, leading to a
-      maximum size for a compiled pattern of around 64K.  This  is
+ CREATING CHARACTER TABLES AT BUILD TIME
-      sufficient  to  handle  all  but the most gigantic patterns.
-      Nevertheless, some people do want to process  enormous  pat-
+        PCRE  uses fixed tables for processing characters whose code values are
-      terns,  so  it is possible to compile PCRE to use three-byte
+        less than 256. By default, PCRE is built with a set of tables that  are
-      or four-byte offsets by adding a setting such as
+        distributed  in  the  file pcre_chartables.c.dist. These tables are for
+        ASCII codes only. If you add
-        --with-link-size=3
+          --enable-rebuild-chartables
-      to the configure command. The value given must be 2,  3,  or
-.  Using  longer  offsets  slows down the operation of PCRE
+        to the configure command, the distributed tables are  no  longer  used.
-      because it has to load additional bytes when handling them.
+        Instead,  a  program  called dftables is compiled and run. This outputs
+        the source for new set of tables, created in the default locale of your
-      If you build PCRE with an increased link size, test  2  (and
+        C runtime system. (This method of replacing the tables does not work if
-      test 5 if you are using UTF-8) will fail. Part of the output
+        you are cross compiling, because dftables is run on the local host.  If
-      of these tests is a representation of the compiled  pattern,
+        you  need  to  create alternative tables when cross compiling, you will
-      and this changes with the link size.
+        have to do so "by hand".)
+ USING EBCDIC CODE
+        PCRE assumes by default that it will run in an  environment  where  the
+        character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
+        This is the case for most computer operating systems.  PCRE  can,  how-
+        ever, be compiled to run in an EBCDIC environment by adding
+          --enable-ebcdic
+        to the configure command. This setting implies --enable-rebuild-charta-
+        bles. You should only use it if you know that  you  are  in  an  EBCDIC
+        environment (for example, an IBM mainframe operating system).
+ PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
+        By default, pcregrep reads all files as plain text. You can build it so
+        that it recognizes files whose names end in .gz or .bz2, and reads them
+        with libz or libbz2, respectively, by adding one or both of
+          --enable-pcregrep-libz
+          --enable-pcregrep-libbz2
+        to the configure command. These options naturally require that the rel-
+        evant libraries are installed on your system. Configuration  will  fail
+        if they are not.
+ PCRETEST OPTION FOR LIBREADLINE SUPPORT
+        If you add
+          --enable-pcretest-libreadline
+        to  the  configure  command,  pcretest  is  linked with the libreadline
+        library, and when its input is from a terminal, it reads it  using  the
+        readline() function. This provides line-editing and history facilities.
+        Note that libreadline is GPL-licenced, so if you distribute a binary of
+        pcretest linked in this way, there may be licensing issues.
+        Setting  this  option  causes  the -lreadline option to be added to the
+        pcretest build. In many operating environments with  a  sytem-installed
+        libreadline this is sufficient. However, in some environments (e.g.  if
+        an unmodified distribution version of readline is in use),  some  extra
+        configuration  may  be necessary. The INSTALL file for libreadline says
+        this:
+          "Readline uses the termcap functions, but does not link with the
+          termcap or curses library itself, allowing applications which link
+          with readline the to choose an appropriate library."
+        If your environment has not been set up so that an appropriate  library
+        is automatically included, you may need to add something like
+          LIBS="-ncurses"
+        immediately before the configure command.
+ SEE ALSO
+        pcreapi(3), pcre_config(3).
+ AUTHOR
+        Philip Hazel
+        University Computing Service
+        Cambridge CB2 3QH, England.
+ REVISION
+        Last updated: 13 April 2008
+        Copyright (c) 1997-2008 University of Cambridge.
+ ------------------------------------------------------------------------------
+ PCREMATCHING(3)                                                PCREMATCHING(3)
- Last updated: 21 January 2003
- Copyright (c) 1997-2003 University of Cambridge.
- -----------------------------------------------------------------------------
  NAME
-      PCRE - Perl-compatible regular expressions
+        PCRE - Perl-compatible regular expressions
+ PCRE MATCHING ALGORITHMS
+        This document describes the two different algorithms that are available
+        in PCRE for matching a compiled regular expression against a given sub-
+        ject  string.  The  "standard"  algorithm  is  the  one provided by the
+        pcre_exec() function.  This works in the same was  as  Perl's  matching
+        function, and provides a Perl-compatible matching operation.
+        An  alternative  algorithm is provided by the pcre_dfa_exec() function;
+        this operates in a different way, and is not  Perl-compatible.  It  has
+        advantages  and disadvantages compared with the standard algorithm, and
+        these are described below.
+        When there is only one possible way in which a given subject string can
+        match  a pattern, the two algorithms give the same answer. A difference
+        arises, however, when there are multiple possibilities. For example, if
+        the pattern
+          ^<.*>
+        is matched against the string
+          <something> <something else> <something further>
+        there are three possible answers. The standard algorithm finds only one
+        of them, whereas the alternative algorithm finds all three.
+ REGULAR EXPRESSIONS AS TREES
+        The set of strings that are matched by a regular expression can be rep-
+        resented  as  a  tree structure. An unlimited repetition in the pattern
+        makes the tree of infinite size, but it is still a tree.  Matching  the
+        pattern  to a given subject string (from a given starting point) can be
+        thought of as a search of the tree.  There are two  ways  to  search  a
+        tree:  depth-first  and  breadth-first, and these correspond to the two
+        matching algorithms provided by PCRE.
- SYNOPSIS OF PCRE API
+ THE STANDARD MATCHING ALGORITHM
-      #include <pcre.h>
+        In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
+        sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
+        depth-first search of the pattern tree. That is, it  proceeds  along  a
+        single path through the tree, checking that the subject matches what is
+        required. When there is a mismatch, the algorithm  tries  any  alterna-
+        tives  at  the  current point, and if they all fail, it backs up to the
+        previous branch point in the  tree,  and  tries  the  next  alternative
+        branch  at  that  level.  This often involves backing up (moving to the
+        left) in the subject string as well.  The  order  in  which  repetition
+        branches  are  tried  is controlled by the greedy or ungreedy nature of
+        the quantifier.
-      pcre *pcre_compile(const char *pattern, int options,
+        If a leaf node is reached, a matching string has  been  found,  and  at
-           const char **errptr, int *erroffset,
+        that  point the algorithm stops. Thus, if there is more than one possi-
-           const unsigned char *tableptr);
+        ble match, this algorithm returns the first one that it finds.  Whether
+        this  is the shortest, the longest, or some intermediate length depends
+        on the way the greedy and ungreedy repetition quantifiers are specified
+        in the pattern.
-      pcre_extra *pcre_study(const pcre *code, int options,
+        Because  it  ends  up  with a single path through the tree, it is rela-
-           const char **errptr);
+        tively straightforward for this algorithm to keep  track  of  the  sub-
+        strings  that  are  matched  by portions of the pattern in parentheses.
+        This provides support for capturing parentheses and back references.
-      int pcre_exec(const pcre *code, const pcre_extra *extra,
-           const char *subject, int length, int startoffset,
-           int options, int *ovector, int ovecsize);
-      int pcre_copy_named_substring(const pcre *code,
+ THE ALTERNATIVE MATCHING ALGORITHM
-           const char *subject, int *ovector,
-           int stringcount, const char *stringname,
-           char *buffer, int buffersize);
-      int pcre_copy_substring(const char *subject, int *ovector,
+        This algorithm conducts a breadth-first search of  the  tree.  Starting
-           int stringcount, int stringnumber, char *buffer,
+        from  the  first  matching  point  in the subject, it scans the subject
-           int buffersize);
+        string from left to right, once, character by character, and as it does
+        this,  it remembers all the paths through the tree that represent valid
+        matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
+        though  it is not implemented as a traditional finite state machine (it
+        keeps multiple states active simultaneously).
-      int pcre_get_named_substring(const pcre *code,
+        The scan continues until either the end of the subject is  reached,  or
-           const char *subject, int *ovector,
+        there  are  no more unterminated paths. At this point, terminated paths
-           int stringcount, const char *stringname,
+        represent the different matching possibilities (if there are none,  the
-           const char **stringptr);
+        match  has  failed).   Thus,  if there is more than one possible match,
+        this algorithm finds all of them, and in particular, it finds the long-
+        est.  In PCRE, there is an option to stop the algorithm after the first
+        match (which is necessarily the shortest) has been found.
-      int pcre_get_stringnumber(const pcre *code,
+        Note that all the matches that are found start at the same point in the
-           const char *name);
+        subject. If the pattern
-      int pcre_get_substring(const char *subject, int *ovector,
+          cat(er(pillar)?)
-           int stringcount, int stringnumber,
-           const char **stringptr);
-      int pcre_get_substring_list(const char *subject,
+        is  matched  against the string "the caterpillar catchment", the result
-           int *ovector, int stringcount, const char ***listptr);
+        will be the three strings "cat", "cater", and "caterpillar" that  start
+        at the fourth character of the subject. The algorithm does not automat-
+        ically move on to find matches that start at later positions.
-      void pcre_free_substring(const char *stringptr);
+        There are a number of features of PCRE regular expressions that are not
+        supported by the alternative matching algorithm. They are as follows:
-      void pcre_free_substring_list(const char **stringptr);
+.  Because  the  algorithm  finds  all possible matches, the greedy or
+        ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
+        ungreedy quantifiers are treated in exactly the same way. However, pos-
+        sessive quantifiers can make a difference when what follows could  also
+        match what is quantified, for example in a pattern like this:
-      const unsigned char *pcre_maketables(void);
+          ^a++\w!
-      int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
+        This  pattern matches "aaab!" but not "aaa!", which would be matched by
-           int what, void *where);
+        a non-possessive quantifier. Similarly, if an atomic group is  present,
+        it  is matched as if it were a standalone pattern at the current point,
+        and the longest match is then "locked in" for the rest of  the  overall
+        pattern.
+. When dealing with multiple paths through the tree simultaneously, it
+        is not straightforward to keep track of  captured  substrings  for  the
+        different  matching  possibilities,  and  PCRE's implementation of this
+        algorithm does not attempt to do this. This means that no captured sub-
+        strings are available.
-      int pcre_info(const pcre *code, int *optptr, *firstcharptr);
+.  Because no substrings are captured, back references within the pat-
+        tern are not supported, and cause errors if encountered.
-      int pcre_config(int what, void *where);
+. For the same reason, conditional expressions that use  a  backrefer-
+        ence  as  the  condition or test for a specific group recursion are not
+        supported.
-      char *pcre_version(void);
+. Because many paths through the tree may be  active,  the  \K  escape
+        sequence, which resets the start of the match when encountered (but may
+        be on some paths and not on others), is not  supported.  It  causes  an
+        error if encountered.
-      void *(*pcre_malloc)(size_t);
+.  Callouts  are  supported, but the value of the capture_top field is
+        always 1, and the value of the capture_last field is always -1.
-      void (*pcre_free)(void *);
+. The \C escape sequence, which (in the standard algorithm) matches  a
+        single  byte, even in UTF-8 mode, is not supported because the alterna-
+        tive algorithm moves through the subject  string  one  character  at  a
+        time, for all active paths through the tree.
-      int (*pcre_callout)(pcre_callout_block *);
+.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
+        are not supported. (*FAIL) is supported, and  behaves  like  a  failing
+        negative assertion.
- PCRE API
+ ADVANTAGES OF THE ALTERNATIVE ALGORITHM
-      PCRE has its own native API,  which  is  described  in  this
+        Using  the alternative matching algorithm provides the following advan-
-      document.  There  is  also  a  set of wrapper functions that
+        tages:
-      correspond to the POSIX regular expression API.   These  are
-      described in the pcreposix documentation.
-      The native API function prototypes are defined in the header
+. All possible matches (at a single point in the subject) are automat-
-      file  pcre.h,  and  on  Unix  systems  the library itself is
+        ically  found,  and  in particular, the longest match is found. To find
-      called libpcre.a, so can be accessed by adding -lpcre to the
+        more than one match using the standard algorithm, you have to do kludgy
-      command  for  linking  an  application  which  calls it. The
+        things with callouts.
-      header file defines the macros PCRE_MAJOR and PCRE_MINOR  to
-      contain the major and minor release numbers for the library.
-      Applications can use these to include support for  different
-      releases.
-      The functions pcre_compile(), pcre_study(), and  pcre_exec()
+.  There is much better support for partial matching. The restrictions
-      are  used  for compiling and matching regular expressions. A
+        on the content of the pattern that apply when using the standard  algo-
-      sample program that demonstrates the simplest way  of  using
+        rithm  for  partial matching do not apply to the alternative algorithm.
-      them  is  given in the file pcredemo.c. The pcresample docu-
+        For non-anchored patterns, the starting position of a partial match  is
-      mentation describes how to run it.
+        available.
-      There are convenience functions for extracting captured sub-
+.  Because  the  alternative  algorithm  scans the subject string just
-      strings from a matched subject string. They are:
+        once, and never needs to backtrack, it is possible to  pass  very  long
+        subject  strings  to  the matching function in several pieces, checking
+        for partial matching each time.
-        pcre_copy_substring()
-        pcre_copy_named_substring()
-        pcre_get_substring()
-        pcre_get_named_substring()
-        pcre_get_substring_list()
-      pcre_free_substring()  and  pcre_free_substring_list()   are
+ DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
-      also  provided,  to  free  the  memory  used  for  extracted
-      strings.
-      The function pcre_maketables() is used (optionally) to build
+        The alternative algorithm suffers from a number of disadvantages:
-      a  set of character tables in the current locale for passing
-      to pcre_compile().
-      The function pcre_fullinfo() is used to find out information
+. It is substantially slower than  the  standard  algorithm.  This  is
-      about a compiled pattern; pcre_info() is an obsolete version
+        partly  because  it has to search for all possible matches, but is also
-      which returns only some of the available information, but is
+        because it is less susceptible to optimization.
-      retained   for   backwards   compatibility.    The  function
-      pcre_version() returns a pointer to a string containing  the
-      version of PCRE and its date of release.
-      The global variables  pcre_malloc  and  pcre_free  initially
+. Capturing parentheses and back references are not supported.
-      contain the entry points of the standard malloc() and free()
-      functions respectively. PCRE  calls  the  memory  management
-      functions  via  these  variables,  so  a calling program can
-      replace them if it  wishes  to  intercept  the  calls.  This
-      should be done before calling any PCRE functions.
-      The global variable pcre_callout initially contains NULL. It
+. Although atomic groups are supported, their use does not provide the
-      can be set by the caller to a "callout" function, which PCRE
+        performance advantage that it does for the standard algorithm.
-      will then call at specified points during a matching  opera-
-      tion. Details are given in the pcrecallout documentation.
+ AUTHOR
+        Philip Hazel
+        University Computing Service
+        Cambridge CB2 3QH, England.
+ REVISION
+        Last updated: 19 April 2008
+        Copyright (c) 1997-2008 University of Cambridge.
+ ------------------------------------------------------------------------------
+ PCREAPI(3)                                                          PCREAPI(3)
+ NAME
+        PCRE - Perl-compatible regular expressions
+ PCRE NATIVE API
+        #include <pcre.h>
+        pcre *pcre_compile(const char *pattern, int options,
+             const char **errptr, int *erroffset,
+             const unsigned char *tableptr);
+        pcre *pcre_compile2(const char *pattern, int options,
+             int *errorcodeptr,
+             const char **errptr, int *erroffset,
+             const unsigned char *tableptr);
+        pcre_extra *pcre_study(const pcre *code, int options,
+             const char **errptr);
+        int pcre_exec(const pcre *code, const pcre_extra *extra,
+             const char *subject, int length, int startoffset,
+             int options, int *ovector, int ovecsize);
+        int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
+             const char *subject, int length, int startoffset,
+             int options, int *ovector, int ovecsize,
+             int *workspace, int wscount);
+        int pcre_copy_named_substring(const pcre *code,
+             const char *subject, int *ovector,
+             int stringcount, const char *stringname,
+             char *buffer, int buffersize);
+        int pcre_copy_substring(const char *subject, int *ovector,
+             int stringcount, int stringnumber, char *buffer,
+             int buffersize);
+        int pcre_get_named_substring(const pcre *code,
+             const char *subject, int *ovector,
+             int stringcount, const char *stringname,
+             const char **stringptr);
+        int pcre_get_stringnumber(const pcre *code,
+             const char *name);
+        int pcre_get_stringtable_entries(const pcre *code,
+             const char *name, char **first, char **last);
+        int pcre_get_substring(const char *subject, int *ovector,
+             int stringcount, int stringnumber,
+             const char **stringptr);
+        int pcre_get_substring_list(const char *subject,
+             int *ovector, int stringcount, const char ***listptr);
+        void pcre_free_substring(const char *stringptr);
+        void pcre_free_substring_list(const char **stringptr);
+        const unsigned char *pcre_maketables(void);
+        int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
+             int what, void *where);
+        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
+        int pcre_refcount(pcre *code, int adjust);
+        int pcre_config(int what, void *where);
+        char *pcre_version(void);
+        void *(*pcre_malloc)(size_t);
+        void (*pcre_free)(void *);
+        void *(*pcre_stack_malloc)(size_t);
+        void (*pcre_stack_free)(void *);
+        int (*pcre_callout)(pcre_callout_block *);
+ PCRE API OVERVIEW
+        PCRE has its own native API, which is described in this document. There
+        are also some wrapper functions that correspond to  the  POSIX  regular
+        expression  API.  These  are  described in the pcreposix documentation.
+        Both of these APIs define a set of C function calls. A C++  wrapper  is
+        distributed with PCRE. It is documented in the pcrecpp page.
+        The  native  API  C  function prototypes are defined in the header file
+        pcre.h, and on Unix systems the library itself is called  libpcre.   It
+        can normally be accessed by adding -lpcre to the command for linking an
+        application  that  uses  PCRE.  The  header  file  defines  the  macros
+        PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
+        bers for the library.  Applications can use these  to  include  support
+        for different releases of PCRE.
+        The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
+        pcre_exec() are used for compiling and matching regular expressions  in
+        a  Perl-compatible  manner. A sample program that demonstrates the sim-
+        plest way of using them is provided in the file  called  pcredemo.c  in
+        the  source distribution. The pcresample documentation describes how to
+        compile and run it.
+        A second matching function, pcre_dfa_exec(), which is not Perl-compati-
+        ble,  is  also provided. This uses a different algorithm for the match-
+        ing. The alternative algorithm finds all possible matches (at  a  given
+        point  in  the subject), and scans the subject just once. However, this
+        algorithm does not return captured substrings. A description of the two
+        matching  algorithms and their advantages and disadvantages is given in
+        the pcrematching documentation.
+        In addition to the main compiling and  matching  functions,  there  are
+        convenience functions for extracting captured substrings from a subject
+        string that is matched by pcre_exec(). They are:
+          pcre_copy_substring()
+          pcre_copy_named_substring()
+          pcre_get_substring()
+          pcre_get_named_substring()
+          pcre_get_substring_list()
+          pcre_get_stringnumber()
+          pcre_get_stringtable_entries()
+        pcre_free_substring() and pcre_free_substring_list() are also provided,
+        to free the memory used for extracted strings.
+        The  function  pcre_maketables()  is  used  to build a set of character
+        tables  in  the  current  locale   for   passing   to   pcre_compile(),
+        pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
+        provided for specialist use.  Most  commonly,  no  special  tables  are
+        passed,  in  which case internal tables that are generated when PCRE is
+        built are used.
+        The function pcre_fullinfo() is used to find out  information  about  a
+        compiled  pattern; pcre_info() is an obsolete version that returns only
+        some of the available information, but is retained for  backwards  com-
+        patibility.   The function pcre_version() returns a pointer to a string
+        containing the version of PCRE and its date of release.
+        The function pcre_refcount() maintains a  reference  count  in  a  data
+        block  containing  a compiled pattern. This is provided for the benefit
+        of object-oriented applications.
+        The global variables pcre_malloc and pcre_free  initially  contain  the
+        entry  points  of  the  standard malloc() and free() functions, respec-
+        tively. PCRE calls the memory management functions via these variables,
+        so  a  calling  program  can replace them if it wishes to intercept the
+        calls. This should be done before calling any PCRE functions.
+        The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
+        indirections  to  memory  management functions. These special functions
+        are used only when PCRE is compiled to use  the  heap  for  remembering
+        data, instead of recursive function calls, when running the pcre_exec()
+        function. See the pcrebuild documentation for  details  of  how  to  do
+        this.  It  is  a non-standard way of building PCRE, for use in environ-
+        ments that have limited stacks. Because of the greater  use  of  memory
+        management,  it  runs  more  slowly. Separate functions are provided so
+        that special-purpose external code can be  used  for  this  case.  When
+        used,  these  functions  are always called in a stack-like manner (last
+        obtained, first freed), and always for memory blocks of the same  size.
+        There  is  a discussion about PCRE's stack usage in the pcrestack docu-
+        mentation.
+        The global variable pcre_callout initially contains NULL. It can be set
+        by  the  caller  to  a "callout" function, which PCRE will then call at
+        specified points during a matching operation. Details are given in  the
+        pcrecallout documentation.
+ NEWLINES
+        PCRE  supports five different conventions for indicating line breaks in
+        strings: a single CR (carriage return) character, a  single  LF  (line-
+        feed) character, the two-character sequence CRLF, any of the three pre-
+        ceding, or any Unicode newline sequence. The Unicode newline  sequences
+        are  the  three just mentioned, plus the single characters VT (vertical
+        tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
+        separator, U+2028), and PS (paragraph separator, U+2029).
+        Each  of  the first three conventions is used by at least one operating
+        system as its standard newline sequence. When PCRE is built, a  default
+        can  be  specified.  The default default is LF, which is the Unix stan-
+        dard. When PCRE is run, the default can be overridden,  either  when  a
+        pattern is compiled, or when it is matched.
+        At compile time, the newline convention can be specified by the options
+        argument of pcre_compile(), or it can be specified by special  text  at
+        the start of the pattern itself; this overrides any other settings. See
+        the pcrepattern page for details of the special character sequences.
+        In the PCRE documentation the word "newline" is used to mean "the char-
+        acter  or pair of characters that indicate a line break". The choice of
+        newline convention affects the handling of  the  dot,  circumflex,  and
+        dollar metacharacters, the handling of #-comments in /x mode, and, when
+        CRLF is a recognized line ending sequence, the match position  advance-
+        ment for a non-anchored pattern. There is more detail about this in the
+        section on pcre_exec() options below.
+        The choice of newline convention does not affect the interpretation  of
+        the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
+        which is controlled in a similar way, but by separate options.
  MULTITHREADING
-      The PCRE functions can be used in  multi-threading  applica-
+        The PCRE functions can be used in  multi-threading  applications,  with
-      tions, with the proviso that the memory management functions
+        the  proviso  that  the  memory  management  functions  pointed  to  by
-      pointed to by pcre_malloc and  pcre_free,  and  the  callout
+        pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
-      function  pointed  to  by  pcre_callout,  are  shared by all
+        callout function pointed to by pcre_callout, are shared by all threads.
-      threads.
+        The compiled form of a regular expression is not altered during  match-
-      The compiled form of a regular  expression  is  not  altered
+        ing, so the same compiled pattern can safely be used by several threads
-      during  matching, so the same compiled pattern can safely be
+        at once.
-      used by several threads at once.
+ SAVING PRECOMPILED PATTERNS FOR LATER USE
+        The compiled form of a regular expression can be saved and re-used at a
+        later  time,  possibly by a different program, and even on a host other
+        than the one on which  it  was  compiled.  Details  are  given  in  the
+        pcreprecompile  documentation.  However, compiling a regular expression
+        with one version of PCRE for use with a different version is not  guar-
+        anteed to work and may cause crashes.
  CHECKING BUILD-TIME OPTIONS
-      int pcre_config(int what, void *where);
+        int pcre_config(int what, void *where);
-      The function pcre_config() makes  it  possible  for  a  PCRE
+        The  function pcre_config() makes it possible for a PCRE client to dis-
-      client  to  discover  which optional features have been com-
+        cover which optional features have been compiled into the PCRE library.
-      piled into the PCRE library. The pcrebuild documentation has
+        The  pcrebuild documentation has more details about these optional fea-
-      more details about these optional features.
+        tures.
-      The first argument for pcre_config() is an integer, specify-
+        The first argument for pcre_config() is an  integer,  specifying  which
-      ing  which information is required; the second argument is a
+        information is required; the second argument is a pointer to a variable
-      pointer to a variable into which the information is  placed.
+        into which the information is  placed.  The  following  information  is
-      The following information is available:
+        available:
-        PCRE_CONFIG_UTF8
+          PCRE_CONFIG_UTF8
-      The output is an integer that is set to one if UTF-8 support
+        The  output is an integer that is set to one if UTF-8 support is avail-
-      is available; otherwise it is set to zero.
+        able; otherwise it is set to zero.
-        PCRE_CONFIG_NEWLINE
+          PCRE_CONFIG_UNICODE_PROPERTIES
-      The output is an integer that is set to  the  value  of  the
+        The output is an integer that is set to  one  if  support  for  Unicode
-      code  that  is  used for the newline character. It is either
+        character properties is available; otherwise it is set to zero.
-      linefeed (10) or carriage return (13), and  should  normally
-      be the standard character for your operating system.
-        PCRE_CONFIG_LINK_SIZE
+          PCRE_CONFIG_NEWLINE
-      The output is an integer that contains the number  of  bytes
+        The  output  is  an integer whose value specifies the default character
-      used  for  internal linkage in compiled regular expressions.
+        sequence that is recognized as meaning "newline". The four values  that
-      The value is 2, 3, or 4. Larger values allow larger  regular
+        are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
-      expressions  to be compiled, at the expense of slower match-
+        and -1 for ANY. The default should normally be  the  standard  sequence
-      ing. The default value of 2 is sufficient for  all  but  the
+        for your operating system.
-      most  massive patterns, since it allows the compiled pattern
-      to be up to 64K in size.
-        PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
+          PCRE_CONFIG_BSR
-      The output is an integer that contains the  threshold  above
+        The output is an integer whose value indicates what character sequences
-      which  the POSIX interface uses malloc() for output vectors.
+        the \R escape sequence matches by default. A value of 0 means  that  \R
-      Further details are given in the pcreposix documentation.
+        matches  any  Unicode  line ending sequence; a value of 1 means that \R
+        matches only CR, LF, or CRLF. The default can be overridden when a pat-
+        tern is compiled or matched.
-        PCRE_CONFIG_MATCH_LIMIT
+          PCRE_CONFIG_LINK_SIZE
-      The output is an integer that gives the  default  limit  for
+        The  output  is  an  integer that contains the number of bytes used for
-      the   number  of  internal  matching  function  calls  in  a
+        internal linkage in compiled regular expressions. The value is 2, 3, or
-      pcre_exec()  execution.  Further  details  are  given   with
+.  Larger  values  allow larger regular expressions to be compiled, at
-      pcre_exec() below.
+        the expense of slower matching. The default value of  2  is  sufficient
+        for  all  but  the  most massive patterns, since it allows the compiled
+        pattern to be up to 64K in size.
+          PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
+        The output is an integer that contains the threshold  above  which  the
+        POSIX  interface  uses malloc() for output vectors. Further details are
+        given in the pcreposix documentation.
+          PCRE_CONFIG_MATCH_LIMIT
+        The output is an integer that gives the default limit for the number of
+        internal  matching  function  calls in a pcre_exec() execution. Further
+        details are given with pcre_exec() below.
+          PCRE_CONFIG_MATCH_LIMIT_RECURSION
+        The output is an integer that gives the default limit for the depth  of
+        recursion  when calling the internal matching function in a pcre_exec()
+        execution. Further details are given with pcre_exec() below.
+          PCRE_CONFIG_STACKRECURSE
+        The output is an integer that is set to one if internal recursion  when
+        running pcre_exec() is implemented by recursive function calls that use
+        the stack to remember their state. This is the usual way that  PCRE  is
+        compiled. The output is zero if PCRE was compiled to use blocks of data
+        on the  heap  instead  of  recursive  function  calls.  In  this  case,
+        pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
+        blocks on the heap, thus avoiding the use of the stack.
  COMPILING A PATTERN
-      pcre *pcre_compile(const char *pattern, int options,
+        pcre *pcre_compile(const char *pattern, int options,
-           const char **errptr, int *erroffset,
+             const char **errptr, int *erroffset,
-           const unsigned char *tableptr);
+             const unsigned char *tableptr);
-      The function pcre_compile() is called to compile  a  pattern
+        pcre *pcre_compile2(const char *pattern, int options,
-      into  an internal form. The pattern is a C string terminated
+             int *errorcodeptr,
-      by a binary zero, and is passed in the argument  pattern.  A
+             const char **errptr, int *erroffset,
-      pointer  to  a  single  block of memory that is obtained via
+             const unsigned char *tableptr);
-      pcre_malloc is returned. This contains the compiled code and
-      related  data.  The  pcre  type  is defined for the returned
+        Either of the functions pcre_compile() or pcre_compile2() can be called
-      block; this is a typedef for a structure whose contents  are
+        to compile a pattern into an internal form. The only difference between
-      not  externally  defined. It is up to the caller to free the
+        the two interfaces is that pcre_compile2() has an additional  argument,
-      memory when it is no longer required.
+        errorcodeptr, via which a numerical error code can be returned.
-      Although the compiled code of a PCRE regex  is  relocatable,
+        The pattern is a C string terminated by a binary zero, and is passed in
-      that is, it does not depend on memory location, the complete
+        the pattern argument. A pointer to a single block  of  memory  that  is
-      pcre data block is not fully relocatable,  because  it  con-
+        obtained  via  pcre_malloc is returned. This contains the compiled code
-      tains  a  copy of the tableptr argument, which is an address
+        and related data. The pcre type is defined for the returned block; this
-      (see below).
+        is a typedef for a structure whose contents are not externally defined.
-      The options argument contains independent bits  that  affect
+        It is up to the caller to free the memory (via pcre_free) when it is no
-      the  compilation.  It  should  be  zero  if  no  options are
+        longer required.
-      required. Some of the options, in particular, those that are
-      compatible  with Perl, can also be set and unset from within
+        Although  the compiled code of a PCRE regex is relocatable, that is, it
-      the pattern (see the detailed description of regular expres-
+        does not depend on memory location, the complete pcre data block is not
-      sions  in the pcrepattern documentation). For these options,
+        fully  relocatable, because it may contain a copy of the tableptr argu-
-      the contents of the options argument specifies their initial
+        ment, which is an address (see below).
-      settings  at  the  start  of  compilation and execution. The
-      PCRE_ANCHORED option can be set at the time of  matching  as
+        The options argument contains various bit settings that affect the com-
-      well as at compile time.
+        pilation.  It  should be zero if no options are required. The available
+        options are described below. Some of them, in  particular,  those  that
-      If errptr is NULL, pcre_compile() returns NULL  immediately.
+        are  compatible  with  Perl,  can also be set and unset from within the
-      Otherwise, if compilation of a pattern fails, pcre_compile()
+        pattern (see the detailed description  in  the  pcrepattern  documenta-
-      returns NULL, and sets the variable pointed to by errptr  to
+        tion).  For  these options, the contents of the options argument speci-
-      point  to a textual error message. The offset from the start
+        fies their initial settings at the start of compilation and  execution.
-      of  the  pattern  to  the  character  where  the  error  was
+        The  PCRE_ANCHORED  and PCRE_NEWLINE_xxx options can be set at the time
-      discovered   is   placed  in  the  variable  pointed  to  by
+        of matching as well as at compile time.
-      erroffset, which must not be NULL. If it  is,  an  immediate
-      error is given.
+        If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
+        if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
-      If the final  argument,  tableptr,  is  NULL,  PCRE  uses  a
+        sets the variable pointed to by errptr to point to a textual error mes-
-      default  set  of character tables which are built when it is
+        sage. This is a static string that is part of the library. You must not
-      compiled, using the default C  locale.  Otherwise,  tableptr
+        try to free it. The offset from the start of the pattern to the charac-
-      must  be  the result of a call to pcre_maketables(). See the
+        ter where the error was discovered is placed in the variable pointed to
-      section on locale support below.
+        by erroffset, which must not be NULL. If it is, an immediate  error  is
+        given.
-      This code fragment shows a typical straightforward  call  to
-      pcre_compile():
+        If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
+        codeptr argument is not NULL, a non-zero error code number is  returned
-        pcre *re;
+        via  this argument in the event of an error. This is in addition to the
-        const char *error;
+        textual error message. Error codes and messages are listed below.
-        int erroffset;
-        re = pcre_compile(
+        If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
-          "^A.*Z",          /* the pattern */
+        character  tables  that  are  built  when  PCRE  is compiled, using the
-,                /* default options */
+        default C locale. Otherwise, tableptr must be an address  that  is  the
-          &error,           /* for error message */
+        result  of  a  call to pcre_maketables(). This value is stored with the
-          &erroffset,       /* for error offset */
+        compiled pattern, and used again by pcre_exec(), unless  another  table
-          NULL);            /* use default character tables */
+        pointer is passed to it. For more discussion, see the section on locale
+        support below.
-      The following option bits are defined:
+        This code fragment shows a typical straightforward  call  to  pcre_com-
-        PCRE_ANCHORED
+        pile():
-      If this bit is set, the pattern is forced to be  "anchored",
+          pcre *re;
-      that is, it is constrained to match only at the first match-
+          const char *error;
-      ing point in the string which is being searched  (the  "sub-
+          int erroffset;
-      ject string"). This effect can also be achieved by appropri-
+          re = pcre_compile(
-      ate constructs in the pattern itself, which is the only  way
+            "^A.*Z",          /* the pattern */
-      to do it in Perl.
+,                /* default options */
+            &error,           /* for error message */
-        PCRE_CASELESS
+            &erroffset,       /* for error offset */
+            NULL);            /* use default character tables */
-      If this bit is set, letters in the pattern match both  upper
-      and  lower  case  letters.  It  is  equivalent  to Perl's /i
+        The  following  names  for option bits are defined in the pcre.h header
-      option, and it can be changed within a  pattern  by  a  (?i)
+        file:
-      option setting.
+          PCRE_ANCHORED
-        PCRE_DOLLAR_ENDONLY
+        If this bit is set, the pattern is forced to be "anchored", that is, it
-      If this bit is set, a dollar metacharacter  in  the  pattern
+        is  constrained to match only at the first matching point in the string
-      matches  only at the end of the subject string. Without this
+        that is being searched (the "subject string"). This effect can also  be
-      option, a dollar also matches immediately before  the  final
+        achieved  by appropriate constructs in the pattern itself, which is the
-      character  if it is a newline (but not before any other new-
+        only way to do it in Perl.
-      lines).  The  PCRE_DOLLAR_ENDONLY  option  is   ignored   if
-      PCRE_MULTILINE is set. There is no equivalent to this option
+          PCRE_AUTO_CALLOUT
-      in Perl, and no way to set it within a pattern.
+        If this bit is set, pcre_compile() automatically inserts callout items,
-        PCRE_DOTALL
+        all  with  number  255, before each pattern item. For discussion of the
+        callout facility, see the pcrecallout documentation.
-      If this bit is  set,  a  dot  metacharater  in  the  pattern
-      matches all characters, including newlines. Without it, new-
+          PCRE_BSR_ANYCRLF
-      lines are excluded. This option is equivalent to  Perl's  /s
+          PCRE_BSR_UNICODE
-      option,  and  it  can  be changed within a pattern by a (?s)
-      option setting. A negative class such as [^a] always matches
+        These options (which are mutually exclusive) control what the \R escape
-      a  newline  character,  independent  of  the setting of this
+        sequence  matches.  The choice is either to match only CR, LF, or CRLF,
-      option.
+        or to match any Unicode newline sequence. The default is specified when
+        PCRE is built. It can be overridden from within the pattern, or by set-
-        PCRE_EXTENDED
+        ting an option when a compiled pattern is matched.
-      If this bit is set, whitespace data characters in  the  pat-
+          PCRE_CASELESS
-      tern  are  totally  ignored  except when escaped or inside a
-      character class. Whitespace does not include the VT  charac-
+        If this bit is set, letters in the pattern match both upper  and  lower
-      ter  (code 11). In addition, characters between an unescaped
+        case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
-      # outside a character class and the next newline  character,
+        changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
-      inclusive, are also ignored. This is equivalent to Perl's /x
+        always  understands the concept of case for characters whose values are
-      option, and it can be changed within a  pattern  by  a  (?x)
+        less than 128, so caseless matching is always possible. For  characters
-      option setting.
+        with  higher  values,  the concept of case is supported if PCRE is com-
+        piled with Unicode property support, but not otherwise. If you want  to
-      This option makes it possible  to  include  comments  inside
+        use  caseless  matching  for  characters 128 and above, you must ensure
-      complicated patterns.  Note, however, that this applies only
+        that PCRE is compiled with Unicode property support  as  well  as  with
-      to data characters. Whitespace characters may  never  appear
+        UTF-8 support.
-      within special character sequences in a pattern, for example
-      within the sequence (?( which introduces a conditional  sub-
+          PCRE_DOLLAR_ENDONLY
-      pattern.
+        If  this bit is set, a dollar metacharacter in the pattern matches only
-        PCRE_EXTRA
+        at the end of the subject string. Without this option,  a  dollar  also
+        matches  immediately before a newline at the end of the string (but not
-      This option was invented in  order  to  turn  on  additional
+        before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
-      functionality of PCRE that is incompatible with Perl, but it
+        if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
-      is currently of very little use. When set, any backslash  in
+        Perl, and no way to set it within a pattern.
-      a  pattern  that is followed by a letter that has no special
-      meaning causes an error, thus reserving  these  combinations
+          PCRE_DOTALL
-      for  future  expansion.  By default, as in Perl, a backslash
-      followed by a letter with no special meaning is treated as a
+        If this bit is set, a dot metacharater in the pattern matches all char-
-      literal.  There  are at present no other features controlled
+        acters,  including  those that indicate newline. Without it, a dot does
-      by this option. It can also be set by a (?X) option  setting
+        not match when the current position is at a  newline.  This  option  is
-      within a pattern.
+        equivalent  to Perl's /s option, and it can be changed within a pattern
+        by a (?s) option setting. A negative class such as [^a] always  matches
-        PCRE_MULTILINE
+        newline characters, independent of the setting of this option.
-      By default, PCRE treats the subject string as consisting  of
+          PCRE_DUPNAMES
-      a  single "line" of characters (even if it actually contains
-      several newlines). The "start  of  line"  metacharacter  (^)
+        If  this  bit is set, names used to identify capturing subpatterns need
-      matches  only  at the start of the string, while the "end of
+        not be unique. This can be helpful for certain types of pattern when it
-      line" metacharacter ($) matches  only  at  the  end  of  the
+        is  known  that  only  one instance of the named subpattern can ever be
-      string,    or   before   a   terminating   newline   (unless
+        matched. There are more details of named subpatterns  below;  see  also
-      PCRE_DOLLAR_ENDONLY is set). This is the same as Perl.
+        the pcrepattern documentation.
-      When PCRE_MULTILINE it is set, the "start of line" and  "end
+          PCRE_EXTENDED
-      of  line"  constructs match immediately following or immedi-
-      ately before any newline  in  the  subject  string,  respec-
+        If  this  bit  is  set,  whitespace  data characters in the pattern are
-      tively,  as  well  as  at  the  very  start and end. This is
+        totally ignored except when escaped or inside a character class. White-
-      equivalent to Perl's /m option, and it can be changed within
+        space does not include the VT character (code 11). In addition, charac-
-      a  pattern  by  a  (?m) option setting. If there are no "\n"
+        ters between an unescaped # outside a character class and the next new-
-      characters in a subject string, or no occurrences of ^ or  $
+        line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
-      in a pattern, setting PCRE_MULTILINE has no effect.
+        option, and it can be changed within a pattern by a  (?x)  option  set-
+        ting.
-        PCRE_NO_AUTO_CAPTURE
+        This  option  makes  it possible to include comments inside complicated
-      If this option is set, it disables the use of numbered  cap-
+        patterns.  Note, however, that this applies only  to  data  characters.
-      turing  parentheses  in the pattern. Any opening parenthesis
+        Whitespace   characters  may  never  appear  within  special  character
-      that is not followed by ? behaves as if it were followed  by
+        sequences in a pattern, for  example  within  the  sequence  (?(  which
-      ?:  but  named  parentheses  can still be used for capturing
+        introduces a conditional subpattern.
-      (and they acquire numbers in the usual  way).  There  is  no
-      equivalent of this option in Perl.
+          PCRE_EXTRA
-        PCRE_UNGREEDY
+        This  option  was invented in order to turn on additional functionality
+        of PCRE that is incompatible with Perl, but it  is  currently  of  very
-      This option inverts the "greediness" of the  quantifiers  so
+        little  use. When set, any backslash in a pattern that is followed by a
-      that  they  are  not greedy by default, but become greedy if
+        letter that has no special meaning  causes  an  error,  thus  reserving
-      followed by "?". It is not compatible with Perl. It can also
+        these  combinations  for  future  expansion.  By default, as in Perl, a
-      be set by a (?U) option setting within the pattern.
+        backslash followed by a letter with no special meaning is treated as  a
+        literal.  (Perl can, however, be persuaded to give a warning for this.)
-        PCRE_UTF8
+        There are at present no other features controlled by  this  option.  It
+        can also be set by a (?X) option setting within a pattern.
-      This option causes PCRE to regard both the pattern  and  the
-      subject  as  strings  of UTF-8 characters instead of single-
+          PCRE_FIRSTLINE
-      byte character strings. However, it  is  available  only  if
-      PCRE  has  been  built to include UTF-8 support. If not, the
+        If  this  option  is  set,  an  unanchored pattern is required to match
-      use of this option provokes an error. Details  of  how  this
+        before or at the first  newline  in  the  subject  string,  though  the
-      option  changes  the behaviour of PCRE are given in the sec-
+        matched text may continue over the newline.
-      tion on UTF-8 support in the main pcre page.
+          PCRE_JAVASCRIPT_COMPAT
+        If this option is set, PCRE's behaviour is changed in some ways so that
+        it is compatible with JavaScript rather than Perl. The changes  are  as
+        follows:
+        (1)  A  lone  closing square bracket in a pattern causes a compile-time
+        error, because this is illegal in JavaScript (by default it is  treated
+        as a data character). Thus, the pattern AB]CD becomes illegal when this
+        option is set.
+        (2) At run time, a back reference to an unset subpattern group  matches
+        an  empty  string (by default this causes the current matching alterna-
+        tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
+        set  (assuming  it can find an "a" in the subject), whereas it fails by
+        default, for Perl compatibility.
+          PCRE_MULTILINE
+        By default, PCRE treats the subject string as consisting  of  a  single
+        line  of characters (even if it actually contains newlines). The "start
+        of line" metacharacter (^) matches only at the  start  of  the  string,
+        while  the  "end  of line" metacharacter ($) matches only at the end of
+        the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
+        is set). This is the same as Perl.
+        When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
+        constructs match immediately following or immediately  before  internal
+        newlines  in  the  subject string, respectively, as well as at the very
+        start and end. This is equivalent to Perl's /m option, and  it  can  be
+        changed within a pattern by a (?m) option setting. If there are no new-
+        lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
+        setting PCRE_MULTILINE has no effect.
+          PCRE_NEWLINE_CR
+          PCRE_NEWLINE_LF
+          PCRE_NEWLINE_CRLF
+          PCRE_NEWLINE_ANYCRLF
+          PCRE_NEWLINE_ANY
+        These  options  override the default newline definition that was chosen
+        when PCRE was built. Setting the first or the second specifies  that  a
+        newline  is  indicated  by a single character (CR or LF, respectively).
+        Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
+        two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
+        that any of the three preceding sequences should be recognized. Setting
+        PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
+        recognized. The Unicode newline sequences are the three just mentioned,
+        plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
+        U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
+        (paragraph  separator,  U+2029).  The  last  two are recognized only in
+        UTF-8 mode.
+        The newline setting in the  options  word  uses  three  bits  that  are
+        treated as a number, giving eight possibilities. Currently only six are
+        used (default plus the five values above). This means that if  you  set
+        more  than one newline option, the combination may or may not be sensi-
+        ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
+        PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
+        cause an error.
+        The only time that a line break is specially recognized when  compiling
+        a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
+        character class is encountered. This indicates  a  comment  that  lasts
+        until  after the next line break sequence. In other circumstances, line
+        break  sequences  are  treated  as  literal  data,   except   that   in
+        PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
+        and are therefore ignored.
+        The newline option that is set at compile time becomes the default that
+        is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
+          PCRE_NO_AUTO_CAPTURE
+        If this option is set, it disables the use of numbered capturing paren-
+        theses  in the pattern. Any opening parenthesis that is not followed by
+        ? behaves as if it were followed by ?: but named parentheses can  still
+        be  used  for  capturing  (and  they acquire numbers in the usual way).
+        There is no equivalent of this option in Perl.
+          PCRE_UNGREEDY
+        This option inverts the "greediness" of the quantifiers  so  that  they
+        are  not greedy by default, but become greedy if followed by "?". It is
+        not compatible with Perl. It can also be set by a (?U)  option  setting
+        within the pattern.
+          PCRE_UTF8
+        This  option  causes PCRE to regard both the pattern and the subject as
+        strings of UTF-8 characters instead of single-byte  character  strings.
+        However,  it is available only when PCRE is built to include UTF-8 sup-
+        port. If not, the use of this option provokes an error. Details of  how
+        this  option  changes the behaviour of PCRE are given in the section on
+        UTF-8 support in the main pcre page.
+          PCRE_NO_UTF8_CHECK
+        When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
+        automatically  checked.  There  is  a  discussion about the validity of
+        UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of
+        bytes  is  found,  pcre_compile() returns an error. If you already know
+        that your pattern is valid, and you want to skip this check for perfor-
+        mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is
+        set, the effect of passing an invalid UTF-8  string  as  a  pattern  is
+        undefined.  It  may  cause your program to crash. Note that this option
+        can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
+        UTF-8 validity checking of subject strings.
+ COMPILATION ERROR CODES
+        The  following  table  lists  the  error  codes than may be returned by
+        pcre_compile2(), along with the error messages that may be returned  by
+        both  compiling functions. As PCRE has developed, some error codes have
+        fallen out of use. To avoid confusion, they have not been re-used.
+ no error
+ \ at end of pattern
+ \c at end of pattern
+ unrecognized character follows \
+ numbers out of order in {} quantifier
+ number too big in {} quantifier
+ missing terminating ] for character class
+ invalid escape sequence in character class
+ range out of order in character class
+ nothing to repeat
+ [this code is not in use]
+ internal error: unexpected repeat
+ unrecognized character after (? or (?-
+ POSIX named classes are supported only within a class
+ missing )
+ reference to non-existent subpattern
+ erroffset passed as NULL
+ unknown option bit(s) set
+ missing ) after comment
+ [this code is not in use]
+ regular expression is too large
+ failed to get memory
+ unmatched parentheses
+ internal error: code overflow
+ unrecognized character after (?<
+ lookbehind assertion is not fixed length
+ malformed number or name after (?(
+ conditional group contains more than two branches
+ assertion expected after (?(
+ (?R or (?[+-]digits must be followed by )
+ unknown POSIX class name
+ POSIX collating elements are not supported
+ this version of PCRE is not compiled with PCRE_UTF8 support
+ [this code is not in use]
+ character value in \x{...} sequence is too large
+ invalid condition (?(0)
+ \C not allowed in lookbehind assertion
+ PCRE does not support \L, \l, \N, \U, or \u
+ number after (?C is > 255
+ closing ) for (?C expected
+ recursive call could loop indefinitely
+ unrecognized character after (?P
+ syntax error in subpattern name (missing terminator)
+ two named subpatterns have the same name
+ invalid UTF-8 string
+ support for \P, \p, and \X has not been compiled
+ malformed \P or \p sequence
+ unknown property name after \P or \p
+ subpattern name is too long (maximum 32 characters)
+ too many named subpatterns (maximum 10000)
+ [this code is not in use]
+ octal value is greater than \377 (not in UTF-8 mode)
+ internal error: overran compiling workspace
+ internal  error:  previously-checked  referenced  subpattern  not
+        found
+ DEFINE group contains more than one branch
+ repeating a DEFINE group is not allowed
+ inconsistent NEWLINE options
+ \g is not followed by a braced, angle-bracketed, or quoted
+                name/number or by a plain number
+ a numbered reference must not be zero
+ (*VERB) with an argument is not supported
+ (*VERB) not recognized
+ number is too big
+ subpattern name expected
+ digit expected after (?+
+ ] is an invalid data character in JavaScript compatibility mode
+        The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
+        values may be used if the limits were changed when PCRE was built.
  STUDYING A PATTERN
-      pcre_extra *pcre_study(const pcre *code, int options,
+        pcre_extra *pcre_study(const pcre *code, int options
-           const char **errptr);
+             const char **errptr);
-      When a pattern is going to be  used  several  times,  it  is
+        If a compiled pattern is going to be used several times,  it  is  worth
-      worth  spending  more time analyzing it in order to speed up
+        spending more time analyzing it in order to speed up the time taken for
-      the time taken for matching. The function pcre_study() takes
+        matching. The function pcre_study() takes a pointer to a compiled  pat-
-      a  pointer  to  a compiled pattern as its first argument. If
+        tern as its first argument. If studying the pattern produces additional
-      studing the pattern  produces  additional  information  that
+        information that will help speed up matching,  pcre_study()  returns  a
-      will  help speed up matching, pcre_study() returns a pointer
+        pointer  to a pcre_extra block, in which the study_data field points to
-      to a pcre_extra block, in which the study_data field  points
+        the results of the study.
-      to the results of the study.
+        The  returned  value  from  pcre_study()  can  be  passed  directly  to
-      The  returned  value  from  a  pcre_study()  can  be  passed
+        pcre_exec().  However,  a  pcre_extra  block also contains other fields
-      directly  to pcre_exec(). However, the pcre_extra block also
+        that can be set by the caller before the block  is  passed;  these  are
-      contains other fields that can be set by the  caller  before
+        described below in the section on matching a pattern.
-      the  block is passed; these are described below. If studying
-      the pattern does not  produce  any  additional  information,
+        If  studying  the  pattern  does not produce any additional information
-      pcre_study() returns NULL. In that circumstance, if the cal-
+        pcre_study() returns NULL. In that circumstance, if the calling program
-      ling program wants to pass  some  of  the  other  fields  to
+        wants  to  pass  any of the other fields to pcre_exec(), it must set up
-      pcre_exec(), it must set up its own pcre_extra block.
+        its own pcre_extra block.
-      The second argument contains option  bits.  At  present,  no
+        The second argument of pcre_study() contains option bits.  At  present,
-      options  are  defined  for  pcre_study(),  and this argument
+        no options are defined, and this argument should always be zero.
-      should always be zero.
+        The  third argument for pcre_study() is a pointer for an error message.
-      The third argument for pcre_study()  is  a  pointer  for  an
+        If studying succeeds (even if no data is  returned),  the  variable  it
-      error  message.  If  studying  succeeds  (even if no data is
+        points  to  is  set  to NULL. Otherwise it is set to point to a textual
-      returned), the variable it points to is set to NULL.  Other-
+        error message. This is a static string that is part of the library. You
-      wise it points to a textual error message. You should there-
+        must  not  try  to  free it. You should test the error pointer for NULL
-      fore  test  the  error  pointer  for  NULL   after   calling
+        after calling pcre_study(), to be sure that it has run successfully.
-      pcre_study(), to be sure that it has run successfully.
+        This is a typical call to pcre_study():
-      This is a typical call to pcre_study():
+          pcre_extra *pe;
-        pcre_extra *pe;
+          pe = pcre_study(
-        pe = pcre_study(
+            re,             /* result of pcre_compile() */
-          re,             /* result of pcre_compile() */
+,              /* no options exist */
-,              /* no options exist */
+            &error);        /* set to NULL or points to a message */
-          &error);        /* set to NULL or points to a message */
+        At present, studying a pattern is useful only for non-anchored patterns
-      At present, studying a  pattern  is  useful  only  for  non-
+        that  do not have a single fixed starting character. A bitmap of possi-
-      anchored  patterns  that do not have a single fixed starting
+        ble starting bytes is created.
-      character. A  bitmap  of  possible  starting  characters  is
-      created.
  LOCALE SUPPORT
-      PCRE handles caseless matching, and determines whether char-
+        PCRE handles caseless matching, and determines whether  characters  are
-      acters  are  letters, digits, or whatever, by reference to a
+        letters,  digits, or whatever, by reference to a set of tables, indexed
-      set of tables. When running in UTF-8 mode, this applies only
+        by character value. When running in UTF-8 mode, this  applies  only  to
-      to characters with codes less than 256. The library contains
+        characters  with  codes  less than 128. Higher-valued codes never match
-      a default set of tables that is created  in  the  default  C
+        escapes such as \w or \d, but can be tested with \p if  PCRE  is  built
-      locale  when  PCRE  is compiled. This is used when the final
+        with  Unicode  character property support. The use of locales with Uni-
-      argument of pcre_compile() is NULL, and  is  sufficient  for
+        code is discouraged. If you are handling characters with codes  greater
-      many applications.
+        than  128, you should either use UTF-8 and Unicode, or use locales, but
+        not try to mix the two.
-      An alternative set of tables can, however, be supplied. Such
-      tables  are built by calling the pcre_maketables() function,
+        PCRE contains an internal set of tables that are used  when  the  final
-      which has no arguments, in the relevant locale.  The  result
+        argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
-      can  then be passed to pcre_compile() as often as necessary.
+        applications.  Normally, the internal tables recognize only ASCII char-
-      For example, to build and use tables  that  are  appropriate
+        acters. However, when PCRE is built, it is possible to cause the inter-
-      for  the French locale (where accented characters with codes
+        nal tables to be rebuilt in the default "C" locale of the local system,
-      greater than 128 are treated as letters), the following code
+        which may cause them to be different.
-      could be used:
+        The  internal tables can always be overridden by tables supplied by the
-        setlocale(LC_CTYPE, "fr");
+        application that calls PCRE. These may be created in a different locale
-        tables = pcre_maketables();
+        from  the  default.  As more and more applications change to using Uni-
-        re = pcre_compile(..., tables);
+        code, the need for this locale support is expected to die away.
-      The  tables  are  built  in  memory  that  is  obtained  via
+        External tables are built by calling  the  pcre_maketables()  function,
-      pcre_malloc.  The  pointer that is passed to pcre_compile is
+        which  has no arguments, in the relevant locale. The result can then be
-      saved with the compiled pattern, and  the  same  tables  are
+        passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
-      used via this pointer by pcre_study() and pcre_exec(). Thus,
+        example,  to  build  and use tables that are appropriate for the French
-      for any single pattern, compilation, studying  and  matching
+        locale (where accented characters with  values  greater  than  128  are
-      all happen in the same locale, but different patterns can be
+        treated as letters), the following code could be used:
-      compiled in different locales. It is the caller's  responsi-
-      bility  to  ensure  that  the  memory  containing the tables
+          setlocale(LC_CTYPE, "fr_FR");
-      remains available for as long as it is needed.
+          tables = pcre_maketables();
+          re = pcre_compile(..., tables);
+        The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
+        if you are using Windows, the name for the French locale is "french".
+        When pcre_maketables() runs, the tables are built  in  memory  that  is
+        obtained  via  pcre_malloc. It is the caller's responsibility to ensure
+        that the memory containing the tables remains available for as long  as
+        it is needed.
+        The pointer that is passed to pcre_compile() is saved with the compiled
+        pattern, and the same tables are used via this pointer by  pcre_study()
+        and normally also by pcre_exec(). Thus, by default, for any single pat-
+        tern, compilation, studying and matching all happen in the same locale,
+        but different patterns can be compiled in different locales.
+        It  is  possible to pass a table pointer or NULL (indicating the use of
+        the internal tables) to pcre_exec(). Although  not  intended  for  this
+        purpose,  this facility could be used to match a pattern in a different
+        locale from the one in which it was compiled. Passing table pointers at
+        run time is discussed below in the section on matching a pattern.
  INFORMATION ABOUT A PATTERN
-      int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
+        int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
-           int what, void *where);
+             int what, void *where);
-      The pcre_fullinfo() function  returns  information  about  a
+        The  pcre_fullinfo() function returns information about a compiled pat-
-      compiled pattern. It replaces the obsolete pcre_info() func-
+        tern. It replaces the obsolete pcre_info() function, which is neverthe-
-      tion, which is nevertheless retained for backwards compabil-
+        less retained for backwards compability (and is documented below).
-      ity (and is documented below).
+        The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
-      The first argument for pcre_fullinfo() is a pointer  to  the
+        pattern. The second argument is the result of pcre_study(), or NULL  if
-      compiled  pattern.  The  second  argument  is  the result of
+        the  pattern  was not studied. The third argument specifies which piece
-      pcre_study(), or NULL if the pattern was  not  studied.  The
+        of information is required, and the fourth argument is a pointer  to  a
-      third  argument  specifies  which  piece  of  information is
+        variable  to  receive  the  data. The yield of the function is zero for
-      required, and the fourth argument is a pointer to a variable
+        success, or one of the following negative numbers:
-      to  receive  the data. The yield of the function is zero for
-      success, or one of the following negative numbers:
+          PCRE_ERROR_NULL       the argument code was NULL
+                                the argument where was NULL
-        PCRE_ERROR_NULL       the argument code was NULL
+          PCRE_ERROR_BADMAGIC   the "magic number" was not found
-                              the argument where was NULL
+          PCRE_ERROR_BADOPTION  the value of what was invalid
-        PCRE_ERROR_BADMAGIC   the "magic number" was not found
-        PCRE_ERROR_BADOPTION  the value of what was invalid
+        The "magic number" is placed at the start of each compiled  pattern  as
+        an  simple check against passing an arbitrary memory pointer. Here is a
-      Here is a typical call of  pcre_fullinfo(),  to  obtain  the
+        typical call of pcre_fullinfo(), to obtain the length of  the  compiled
-      length of the compiled pattern:
+        pattern:
-        int rc;
+          int rc;
-        unsigned long int length;
+          size_t length;
-        rc = pcre_fullinfo(
+          rc = pcre_fullinfo(
-          re,               /* result of pcre_compile() */
+            re,               /* result of pcre_compile() */
-          pe,               /* result of pcre_study(), or NULL */
+            pe,               /* result of pcre_study(), or NULL */
-          PCRE_INFO_SIZE,   /* what is required */
+            PCRE_INFO_SIZE,   /* what is required */
-          &length);         /* where to put the data */
+            &length);         /* where to put the data */
-      The possible values for the third argument  are  defined  in
+        The  possible  values for the third argument are defined in pcre.h, and
-      pcre.h, and are as follows:
+        are as follows:
-        PCRE_INFO_BACKREFMAX
+          PCRE_INFO_BACKREFMAX
-      Return the number of the highest back reference in the  pat-
+        Return the number of the highest back reference  in  the  pattern.  The
-      tern.  The  fourth argument should point to an int variable.
+        fourth  argument  should  point to an int variable. Zero is returned if
-      Zero is returned if there are no back references.
+        there are no back references.
-        PCRE_INFO_CAPTURECOUNT
+          PCRE_INFO_CAPTURECOUNT
-      Return the number of capturing subpatterns in  the  pattern.
+        Return the number of capturing subpatterns in the pattern.  The  fourth
-      The fourth argument should point to an int variable.
+        argument should point to an int variable.
-        PCRE_INFO_FIRSTBYTE
+          PCRE_INFO_DEFAULT_TABLES
-      Return information about  the  first  byte  of  any  matched
+        Return  a pointer to the internal default character tables within PCRE.
-      string,  for a non-anchored pattern. (This option used to be
+        The fourth argument should point to an unsigned char *  variable.  This
-      called PCRE_INFO_FIRSTCHAR; the old name is still recognized
+        information call is provided for internal use by the pcre_study() func-
-      for backwards compatibility.)
+        tion. External callers can cause PCRE to use  its  internal  tables  by
+        passing a NULL table pointer.
-      If there is a fixed first byte, e.g. from a pattern such  as
-      (cat|cow|coyote),  it  is returned in the integer pointed to
+          PCRE_INFO_FIRSTBYTE
-      by where. Otherwise, if either
+        Return  information  about  the first byte of any matched string, for a
-      (a) the pattern was compiled with the PCRE_MULTILINE option,
+        non-anchored pattern. The fourth argument should point to an int  vari-
-      and every branch starts with "^", or
+        able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
+        is still recognized for backwards compatibility.)
-      (b) every  branch  of  the  pattern  starts  with  ".*"  and
-      PCRE_DOTALL is not set (if it were set, the pattern would be
+        If there is a fixed first byte, for example, from  a  pattern  such  as
-      anchored),
+        (cat|cow|coyote), its value is returned. Otherwise, if either
-      -1 is returned, indicating that the pattern matches only  at
+        (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
-      the  start  of  a subject string or after any newline within
+        branch starts with "^", or
-      the string. Otherwise -2 is returned. For anchored patterns,
-      -2 is returned.
+        (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
+        set (if it were set, the pattern would be anchored),
-        PCRE_INFO_FIRSTTABLE
+        -1  is  returned, indicating that the pattern matches only at the start
-      If the pattern was studied, and this resulted  in  the  con-
+        of a subject string or after any newline within the  string.  Otherwise
-      struction of a 256-bit table indicating a fixed set of bytes
+        -2 is returned. For anchored patterns, -2 is returned.
-      for the first byte in any matching string, a pointer to  the
-      table  is  returned.  Otherwise NULL is returned. The fourth
+          PCRE_INFO_FIRSTTABLE
-      argument should point to an unsigned char * variable.
+        If  the pattern was studied, and this resulted in the construction of a
-        PCRE_INFO_LASTLITERAL
+-bit table indicating a fixed set of bytes for the first byte in any
+        matching  string, a pointer to the table is returned. Otherwise NULL is
-      Return the value of the rightmost  literal  byte  that  must
+        returned. The fourth argument should point to an unsigned char *  vari-
-      exist  in  any  matched  string, other than at its start, if
+        able.
-      such a byte has been recorded. The  fourth  argument  should
-      point  to  an  int variable. If there is no such byte, -1 is
+          PCRE_INFO_HASCRORLF
-      returned. For anchored patterns,  a  last  literal  byte  is
-      recorded  only  if  it follows something of variable length.
+        Return  1  if  the  pattern  contains any explicit matches for CR or LF
-      For example, for the pattern /^a\d+z\d+/ the returned  value
+        characters, otherwise 0. The fourth argument should  point  to  an  int
-      is "z", but for /^a\dz\d/ the returned value is -1.
+        variable.  An explicit match is either a literal CR or LF character, or
+        \r or \n.
-        PCRE_INFO_NAMECOUNT
-        PCRE_INFO_NAMEENTRYSIZE
+          PCRE_INFO_JCHANGED
-        PCRE_INFO_NAMETABLE
+        Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
-      PCRE supports the use of named as well as numbered capturing
+        otherwise  0. The fourth argument should point to an int variable. (?J)
-      parentheses. The names are just an additional way of identi-
+        and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
-      fying the parentheses,  which  still  acquire  a  number.  A
-      caller  that  wants  to extract data from a named subpattern
+          PCRE_INFO_LASTLITERAL
-      must convert the name to a number in  order  to  access  the
-      correct  pointers  in  the  output  vector  (described  with
+        Return the value of the rightmost literal byte that must exist  in  any
-      pcre_exec() below). In order to do this, it must  first  use
+        matched  string,  other  than  at  its  start,  if such a byte has been
-      these  three  values  to  obtain  the name-to-number mapping
+        recorded. The fourth argument should point to an int variable. If there
-      table for the pattern.
+        is  no such byte, -1 is returned. For anchored patterns, a last literal
+        byte is recorded only if it follows something of variable  length.  For
-      The  map  consists  of  a  number  of  fixed-size   entries.
+        example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
-      PCRE_INFO_NAMECOUNT   gives   the  number  of  entries,  and
+        /^a\dz\d/ the returned value is -1.
-      PCRE_INFO_NAMEENTRYSIZE gives the size of each  entry;  both
-      of  these return an int value. The entry size depends on the
+          PCRE_INFO_NAMECOUNT
-      length of the longest name.  PCRE_INFO_NAMETABLE  returns  a
+          PCRE_INFO_NAMEENTRYSIZE
-      pointer to the first entry of the table (a pointer to char).
+          PCRE_INFO_NAMETABLE
-      The first two bytes of each entry are the number of the cap-
-      turing parenthesis, most significant byte first. The rest of
+        PCRE supports the use of named as well as numbered capturing  parenthe-
-      the entry is the corresponding name,  zero  terminated.  The
+        ses.  The names are just an additional way of identifying the parenthe-
-      names  are  in alphabetical order. For example, consider the
+        ses, which still acquire numbers. Several convenience functions such as
-      following pattern (assume PCRE_EXTENDED  is  set,  so  white
+        pcre_get_named_substring()  are  provided  for extracting captured sub-
-      space - including newlines - is ignored):
+        strings by name. It is also possible to extract the data  directly,  by
+        first  converting  the  name to a number in order to access the correct
-        (?P<date> (?P<year>(\d\d)?\d\d) -
+        pointers in the output vector (described with pcre_exec() below). To do
-        (?P<month>\d\d) - (?P<day>\d\d) )
+        the  conversion,  you  need  to  use  the  name-to-number map, which is
+        described by these three values.
-      There are four named subpatterns,  so  the  table  has  four
-      entries,  and  each  entry in the table is eight bytes long.
+        The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
-      The table is as follows, with non-printing  bytes  shows  in
+        gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
-      hex, and undefined bytes shown as ??:
+        of each entry; both of these  return  an  int  value.  The  entry  size
+        depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
-01 d  a  t  e  00 ??
+        a pointer to the first entry of the table  (a  pointer  to  char).  The
-05 d  a  y  00 ?? ??
+        first two bytes of each entry are the number of the capturing parenthe-
-04 m  o  n  t  h  00
+        sis, most significant byte first. The rest of the entry is  the  corre-
-02 y  e  a  r  00 ??
+        sponding  name,  zero  terminated. The names are in alphabetical order.
+        When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
-      When writing code to extract data  from  named  subpatterns,
+        theses  numbers.  For  example,  consider the following pattern (assume
-      remember  that the length of each entry may be different for
+        PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
-      each compiled pattern.
+        ignored):
-        PCRE_INFO_OPTIONS
+          (?<date> (?<year>(\d\d)?\d\d) -
+          (?<month>\d\d) - (?<day>\d\d) )
-      Return a copy of the options with which the pattern was com-
-      piled.  The fourth argument should point to an unsigned long
+        There  are  four  named subpatterns, so the table has four entries, and
-      int variable. These option bits are those specified  in  the
+        each entry in the table is eight bytes long. The table is  as  follows,
-      call  to  pcre_compile(),  modified  by any top-level option
+        with non-printing bytes shows in hexadecimal, and undefined bytes shown
-      settings within the pattern itself.
+        as ??:
-      A pattern is automatically anchored by PCRE if  all  of  its
+01 d  a  t  e  00 ??
-      top-level alternatives begin with one of the following:
+05 d  a  y  00 ?? ??
+04 m  o  n  t  h  00
-        ^     unless PCRE_MULTILINE is set
+02 y  e  a  r  00 ??
-        \A    always
-        \G    always
+        When writing code to extract data  from  named  subpatterns  using  the
-        .*    if PCRE_DOTALL is set and there are no back
+        name-to-number  map,  remember that the length of the entries is likely
-                references to the subpattern in which .* appears
+        to be different for each compiled pattern.
-      For such patterns, the  PCRE_ANCHORED  bit  is  set  in  the
+          PCRE_INFO_OKPARTIAL
-      options returned by pcre_fullinfo().
+        Return 1 if the pattern can be used for partial matching, otherwise  0.
-        PCRE_INFO_SIZE
+        The  fourth  argument  should point to an int variable. The pcrepartial
+        documentation lists the restrictions that apply to patterns  when  par-
-      Return the size of the compiled pattern, that is, the  value
+        tial matching is used.
-      that  was  passed as the argument to pcre_malloc() when PCRE
-      was getting memory in which to place the compiled data.  The
+          PCRE_INFO_OPTIONS
-      fourth argument should point to a size_t variable.
+        Return  a  copy of the options with which the pattern was compiled. The
-        PCRE_INFO_STUDYSIZE
+        fourth argument should point to an unsigned long  int  variable.  These
+        option bits are those specified in the call to pcre_compile(), modified
-      Returns the size  of  the  data  block  pointed  to  by  the
+        by any top-level option settings at the start of the pattern itself. In
-      study_data  field  in a pcre_extra block. That is, it is the
+        other  words,  they are the options that will be in force when matching
-      value that was passed to pcre_malloc() when PCRE was getting
+        starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
-      memory into which to place the data created by pcre_study().
+        the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
-      The fourth argument should point to a size_t variable.
+        and PCRE_EXTENDED.
+        A pattern is automatically anchored by PCRE if  all  of  its  top-level
+        alternatives begin with one of the following:
+          ^     unless PCRE_MULTILINE is set
+          \A    always
+          \G    always
+          .*    if PCRE_DOTALL is set and there are no back
+                  references to the subpattern in which .* appears
+        For such patterns, the PCRE_ANCHORED bit is set in the options returned
+        by pcre_fullinfo().
+          PCRE_INFO_SIZE
+        Return the size of the compiled pattern, that is, the  value  that  was
+        passed as the argument to pcre_malloc() when PCRE was getting memory in
+        which to place the compiled data. The fourth argument should point to a
+        size_t variable.
+          PCRE_INFO_STUDYSIZE
+        Return the size of the data block pointed to by the study_data field in
+        a pcre_extra block. That is,  it  is  the  value  that  was  passed  to
+        pcre_malloc() when PCRE was getting memory into which to place the data
+        created by pcre_study(). The fourth argument should point to  a  size_t
+        variable.
  OBSOLETE INFO FUNCTION
-      int pcre_info(const pcre *code, int *optptr, *firstcharptr);
+        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
-      The pcre_info() function is now obsolete because its  inter-
+        The  pcre_info()  function is now obsolete because its interface is too
-      face  is  too  restrictive  to return all the available data
+        restrictive to return all the available data about a compiled  pattern.
-      about  a  compiled  pattern.   New   programs   should   use
+        New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
-      pcre_fullinfo()  instead.  The  yield  of pcre_info() is the
+        pcre_info() is the number of capturing subpatterns, or one of the  fol-
-      number of capturing subpatterns, or  one  of  the  following
+        lowing negative numbers:
-      negative numbers:
+          PCRE_ERROR_NULL       the argument code was NULL
-        PCRE_ERROR_NULL       the argument code was NULL
+          PCRE_ERROR_BADMAGIC   the "magic number" was not found
-        PCRE_ERROR_BADMAGIC   the "magic number" was not found
+        If  the  optptr  argument is not NULL, a copy of the options with which
-      If the optptr argument is not NULL, a copy  of  the  options
+        the pattern was compiled is placed in the integer  it  points  to  (see
-      with which the pattern was compiled is placed in the integer
+        PCRE_INFO_OPTIONS above).
-      it points to (see PCRE_INFO_OPTIONS above).
+        If  the  pattern  is  not anchored and the firstcharptr argument is not
-      If the pattern is not anchored and the firstcharptr argument
+        NULL, it is used to pass back information about the first character  of
-      is  not  NULL, it is used to pass back information about the
+        any matched string (see PCRE_INFO_FIRSTBYTE above).
-      first    character    of    any    matched    string    (see
-      PCRE_INFO_FIRSTBYTE above).
+ REFERENCE COUNTS
+        int pcre_refcount(pcre *code, int adjust);
+        The  pcre_refcount()  function is used to maintain a reference count in
+        the data block that contains a compiled pattern. It is provided for the
+        benefit  of  applications  that  operate  in an object-oriented manner,
+        where different parts of the application may be using the same compiled
+        pattern, but you want to free the block when they are all done.
+        When a pattern is compiled, the reference count field is initialized to
+        zero.  It is changed only by calling this function, whose action is  to
+        add  the  adjust  value  (which may be positive or negative) to it. The
+        yield of the function is the new value. However, the value of the count
+        is  constrained to lie between 0 and 65535, inclusive. If the new value
+        is outside these limits, it is forced to the appropriate limit value.
+        Except when it is zero, the reference count is not correctly  preserved
+        if  a  pattern  is  compiled on one host and then transferred to a host
+        whose byte-order is different. (This seems a highly unlikely scenario.)
+ MATCHING A PATTERN: THE TRADITIONAL FUNCTION
+        int pcre_exec(const pcre *code, const pcre_extra *extra,
+             const char *subject, int length, int startoffset,
+             int options, int *ovector, int ovecsize);
+        The  function pcre_exec() is called to match a subject string against a
+        compiled pattern, which is passed in the code argument. If the  pattern
+        has been studied, the result of the study should be passed in the extra
+        argument. This function is the main matching facility of  the  library,
+        and it operates in a Perl-like manner. For specialist use there is also
+        an alternative matching function, which is described below in the  sec-
+        tion about the pcre_dfa_exec() function.
+        In  most applications, the pattern will have been compiled (and option-
+        ally studied) in the same process that calls pcre_exec().  However,  it
+        is possible to save compiled patterns and study data, and then use them
+        later in different processes, possibly even on different hosts.  For  a
+        discussion about this, see the pcreprecompile documentation.
+        Here is an example of a simple call to pcre_exec():
+          int rc;
+          int ovector[30];
+          rc = pcre_exec(
+            re,             /* result of pcre_compile() */
+            NULL,           /* we didn't study the pattern */
+            "some string",  /* the subject string */
+,             /* the length of the subject string */
+,              /* start at offset 0 in the subject */
+,              /* default options */
+            ovector,        /* vector of integers for substring information */
+);            /* number of elements (NOT size in bytes) */
+    Extra data for pcre_exec()
+        If  the  extra argument is not NULL, it must point to a pcre_extra data
+        block. The pcre_study() function returns such a block (when it  doesn't
+        return  NULL), but you can also create one for yourself, and pass addi-
+        tional information in it. The pcre_extra block contains  the  following
+        fields (not necessarily in this order):
+          unsigned long int flags;
+          void *study_data;
+          unsigned long int match_limit;
+          unsigned long int match_limit_recursion;
+          void *callout_data;
+          const unsigned char *tables;
+        The  flags  field  is a bitmap that specifies which of the other fields
+        are set. The flag bits are:
+          PCRE_EXTRA_STUDY_DATA
+          PCRE_EXTRA_MATCH_LIMIT
+          PCRE_EXTRA_MATCH_LIMIT_RECURSION
+          PCRE_EXTRA_CALLOUT_DATA
+          PCRE_EXTRA_TABLES
+        Other flag bits should be set to zero. The study_data field is  set  in
+        the  pcre_extra  block  that is returned by pcre_study(), together with
+        the appropriate flag bit. You should not set this yourself, but you may
+        add  to  the  block by setting the other fields and their corresponding
+        flag bits.
+        The match_limit field provides a means of preventing PCRE from using up
+        a  vast amount of resources when running patterns that are not going to
+        match, but which have a very large number  of  possibilities  in  their
+        search  trees.  The  classic  example  is  the  use of nested unlimited
+        repeats.
+        Internally, PCRE uses a function called match() which it calls  repeat-
+        edly  (sometimes  recursively). The limit set by match_limit is imposed
+        on the number of times this function is called during  a  match,  which
+        has  the  effect  of  limiting the amount of backtracking that can take
+        place. For patterns that are not anchored, the count restarts from zero
+        for each position in the subject string.
+        The  default  value  for  the  limit can be set when PCRE is built; the
+        default default is 10 million, which handles all but the  most  extreme
+        cases.  You  can  override  the  default by suppling pcre_exec() with a
+        pcre_extra    block    in    which    match_limit    is    set,     and
+        PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
+        exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
+        The match_limit_recursion field is similar to match_limit, but  instead
+        of limiting the total number of times that match() is called, it limits
+        the depth of recursion. The recursion depth is a  smaller  number  than
+        the  total number of calls, because not all calls to match() are recur-
+        sive.  This limit is of use only if it is set smaller than match_limit.
+        Limiting  the  recursion  depth  limits the amount of stack that can be
+        used, or, when PCRE has been compiled to use memory on the heap instead
+        of the stack, the amount of heap memory that can be used.
+        The  default  value  for  match_limit_recursion can be set when PCRE is
+        built; the default default  is  the  same  value  as  the  default  for
+        match_limit.  You can override the default by suppling pcre_exec() with
+        a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
+        PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
+        limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
+        The pcre_callout field is used in conjunction with the  "callout"  fea-
+        ture, which is described in the pcrecallout documentation.
+        The  tables  field  is  used  to  pass  a  character  tables pointer to
+        pcre_exec(); this overrides the value that is stored with the  compiled
+        pattern.  A  non-NULL value is stored with the compiled pattern only if
+        custom tables were supplied to pcre_compile() via  its  tableptr  argu-
+        ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
+        PCRE's internal tables to be used. This facility is  helpful  when  re-
+        using  patterns  that  have been saved after compiling with an external
+        set of tables, because the external tables  might  be  at  a  different
+        address  when  pcre_exec() is called. See the pcreprecompile documenta-
+        tion for a discussion of saving compiled patterns for later use.
+    Option bits for pcre_exec()
+        The unused bits of the options argument for pcre_exec() must  be  zero.
+        The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
+        PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
+        PCRE_PARTIAL.
+          PCRE_ANCHORED
+        The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
+        matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
+        turned  out to be anchored by virtue of its contents, it cannot be made
+        unachored at matching time.
+          PCRE_BSR_ANYCRLF
+          PCRE_BSR_UNICODE
+        These options (which are mutually exclusive) control what the \R escape
+        sequence  matches.  The choice is either to match only CR, LF, or CRLF,
+        or to match any Unicode newline sequence. These  options  override  the
+        choice that was made or defaulted when the pattern was compiled.
+          PCRE_NEWLINE_CR
+          PCRE_NEWLINE_LF
+          PCRE_NEWLINE_CRLF
+          PCRE_NEWLINE_ANYCRLF
+          PCRE_NEWLINE_ANY
+        These  options  override  the  newline  definition  that  was chosen or
+        defaulted when the pattern was compiled. For details, see the  descrip-
+        tion  of  pcre_compile()  above.  During  matching,  the newline choice
+        affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
+        ters.  It may also alter the way the match position is advanced after a
+        match failure for an unanchored pattern.
+        When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
+        set,  and a match attempt for an unanchored pattern fails when the cur-
+        rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
+        explicit  matches  for  CR  or  LF  characters,  the  match position is
+        advanced by two characters instead of one, in other words, to after the
+        CRLF.
+        The above rule is a compromise that makes the most common cases work as
+        expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
+        option is not set), it does not match the string "\r\nA" because, after
+        failing at the start, it skips both the CR and the LF before  retrying.
+        However,  the  pattern  [\r\n]A does match that string, because it con-
+        tains an explicit CR or LF reference, and so advances only by one char-
+        acter after the first failure.
+        An explicit match for CR of LF is either a literal appearance of one of
+        those characters, or one of the \r or  \n  escape  sequences.  Implicit
+        matches  such  as [^X] do not count, nor does \s (which includes CR and
+        LF in the characters that it matches).
+        Notwithstanding the above, anomalous effects may still occur when  CRLF
+        is a valid newline sequence and explicit \r or \n escapes appear in the
+        pattern.
+          PCRE_NOTBOL
+        This option specifies that first character of the subject string is not
+        the  beginning  of  a  line, so the circumflex metacharacter should not
+        match before it. Setting this without PCRE_MULTILINE (at compile  time)
+        causes  circumflex  never to match. This option affects only the behav-
+        iour of the circumflex metacharacter. It does not affect \A.
+          PCRE_NOTEOL
+        This option specifies that the end of the subject string is not the end
+        of  a line, so the dollar metacharacter should not match it nor (except
+        in multiline mode) a newline immediately before it. Setting this  with-
+        out PCRE_MULTILINE (at compile time) causes dollar never to match. This
+        option affects only the behaviour of the dollar metacharacter. It  does
+        not affect \Z or \z.
+          PCRE_NOTEMPTY
+        An empty string is not considered to be a valid match if this option is
+        set. If there are alternatives in the pattern, they are tried.  If  all
+        the  alternatives  match  the empty string, the entire match fails. For
+        example, if the pattern
+          a?b?
+        is applied to a string not beginning with "a" or "b",  it  matches  the
+        empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
+        match is not valid, so PCRE searches further into the string for occur-
+        rences of "a" or "b".
+        Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
+        cial case of a pattern match of the empty  string  within  its  split()
+        function,  and  when  using  the /g modifier. It is possible to emulate
+        Perl's behaviour after matching a null string by first trying the match
+        again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
+        if that fails by advancing the starting offset (see below)  and  trying
+        an ordinary match again. There is some code that demonstrates how to do
+        this in the pcredemo.c sample program.
+          PCRE_NO_UTF8_CHECK
+        When PCRE_UTF8 is set at compile time, the validity of the subject as a
+        UTF-8  string is automatically checked when pcre_exec() is subsequently
+        called.  The value of startoffset is also checked  to  ensure  that  it
+        points  to  the start of a UTF-8 character. There is a discussion about
+        the validity of UTF-8 strings in the section on UTF-8  support  in  the
+        main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
+        pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
+        tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
+        If  you  already  know that your subject is valid, and you want to skip
+        these   checks   for   performance   reasons,   you   can    set    the
+        PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
+        do this for the second and subsequent calls to pcre_exec() if  you  are
+        making  repeated  calls  to  find  all  the matches in a single subject
+        string. However, you should be  sure  that  the  value  of  startoffset
+        points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
+        set, the effect of passing an invalid UTF-8 string as a subject,  or  a
+        value  of startoffset that does not point to the start of a UTF-8 char-
+        acter, is undefined. Your program may crash.
+          PCRE_PARTIAL
+        This option turns on the  partial  matching  feature.  If  the  subject
+        string  fails to match the pattern, but at some point during the match-
+        ing process the end of the subject was reached (that  is,  the  subject
+        partially  matches  the  pattern and the failure to match occurred only
+        because there were not enough subject characters), pcre_exec()  returns
+        PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
+        used, there are restrictions on what may appear in the  pattern.  These
+        are discussed in the pcrepartial documentation.
+    The string to be matched by pcre_exec()
+        The  subject string is passed to pcre_exec() as a pointer in subject, a
+        length in length, and a starting byte offset in startoffset.  In  UTF-8
+        mode,  the  byte  offset  must point to the start of a UTF-8 character.
+        Unlike the pattern string, the subject may contain binary  zero  bytes.
+        When  the starting offset is zero, the search for a match starts at the
+        beginning of the subject, and this is by far the most common case.
+        A non-zero starting offset is useful when searching for  another  match
+        in  the same subject by calling pcre_exec() again after a previous suc-
+        cess.  Setting startoffset differs from just passing over  a  shortened
+        string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
+        with any kind of lookbehind. For example, consider the pattern
+          \Biss\B
+        which finds occurrences of "iss" in the middle of  words.  (\B  matches
+        only  if  the  current position in the subject is not a word boundary.)
+        When applied to the string "Mississipi" the first call  to  pcre_exec()
+        finds  the  first  occurrence. If pcre_exec() is called again with just
+        the remainder of the subject,  namely  "issipi",  it  does  not  match,
+        because \B is always false at the start of the subject, which is deemed
+        to be a word boundary. However, if pcre_exec()  is  passed  the  entire
+        string again, but with startoffset set to 4, it finds the second occur-
+        rence of "iss" because it is able to look behind the starting point  to
+        discover that it is preceded by a letter.
+        If  a  non-zero starting offset is passed when the pattern is anchored,
+        one attempt to match at the given offset is made. This can only succeed
+        if  the  pattern  does  not require the match to be at the start of the
+        subject.
+    How pcre_exec() returns captured substrings
+        In general, a pattern matches a certain portion of the subject, and  in
+        addition,  further  substrings  from  the  subject may be picked out by
+        parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
+        this  is  called "capturing" in what follows, and the phrase "capturing
+        subpattern" is used for a fragment of a pattern that picks out  a  sub-
+        string.  PCRE  supports several other kinds of parenthesized subpattern
+        that do not cause substrings to be captured.
+        Captured substrings are returned to the caller via a vector of  integer
+        offsets  whose  address is passed in ovector. The number of elements in
+        the vector is passed in ovecsize, which must be a non-negative  number.
+        Note: this argument is NOT the size of ovector in bytes.
+        The  first  two-thirds of the vector is used to pass back captured sub-
+        strings, each substring using a pair of integers. The  remaining  third
+        of  the  vector is used as workspace by pcre_exec() while matching cap-
+        turing subpatterns, and is not available for passing back  information.
+        The  length passed in ovecsize should always be a multiple of three. If
+        it is not, it is rounded down.
+        When a match is successful, information about  captured  substrings  is
+        returned  in  pairs  of integers, starting at the beginning of ovector,
+        and continuing up to two-thirds of its length at the  most.  The  first
+        element of a pair is set to the offset of the first character in a sub-
+        string, and the second is set to the  offset  of  the  first  character
+        after  the  end  of  a  substring. The first pair, ovector[0] and ovec-
+        tor[1], identify the portion of  the  subject  string  matched  by  the
+        entire  pattern.  The next pair is used for the first capturing subpat-
+        tern, and so on. The value returned by pcre_exec() is one more than the
+        highest numbered pair that has been set. For example, if two substrings
+        have been captured, the returned value is 3. If there are no  capturing
+        subpatterns,  the return value from a successful match is 1, indicating
+        that just the first pair of offsets has been set.
+        If a capturing subpattern is matched repeatedly, it is the last portion
+        of the string that it matched that is returned.
+        If  the vector is too small to hold all the captured substring offsets,
+        it is used as far as possible (up to two-thirds of its length), and the
+        function  returns a value of zero. In particular, if the substring off-
+        sets are not of interest, pcre_exec() may be called with ovector passed
+        as  NULL  and  ovecsize  as zero. However, if the pattern contains back
+        references and the ovector is not big enough to  remember  the  related
+        substrings,  PCRE has to get additional memory for use during matching.
+        Thus it is usually advisable to supply an ovector.
+        The pcre_info() function can be used to find  out  how  many  capturing
+        subpatterns  there  are  in  a  compiled pattern. The smallest size for
+        ovector that will allow for n captured substrings, in addition  to  the
+        offsets of the substring matched by the whole pattern, is (n+1)*3.
+        It  is  possible for capturing subpattern number n+1 to match some part
+        of the subject when subpattern n has not been used at all. For example,
+        if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
+        return from the function is 4, and subpatterns 1 and 3 are matched, but
+ is  not.  When  this happens, both values in the offset pairs corre-
+        sponding to unused subpatterns are set to -1.
+        Offset values that correspond to unused subpatterns at the end  of  the
+        expression  are  also  set  to  -1. For example, if the string "abc" is
+        matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
+        matched.  The  return  from the function is 2, because the highest used
+        capturing subpattern number is 1. However, you can refer to the offsets
+        for  the  second  and third capturing subpatterns if you wish (assuming
+        the vector is large enough, of course).
+        Some convenience functions are provided  for  extracting  the  captured
+        substrings as separate strings. These are described below.
+    Error return values from pcre_exec()
+        If  pcre_exec()  fails, it returns a negative number. The following are
+        defined in the header file:
+          PCRE_ERROR_NOMATCH        (-1)
+        The subject string did not match the pattern.
+          PCRE_ERROR_NULL           (-2)
+        Either code or subject was passed as NULL,  or  ovector  was  NULL  and
+        ovecsize was not zero.
+          PCRE_ERROR_BADOPTION      (-3)
+        An unrecognized bit was set in the options argument.
+          PCRE_ERROR_BADMAGIC       (-4)
+        PCRE  stores a 4-byte "magic number" at the start of the compiled code,
+        to catch the case when it is passed a junk pointer and to detect when a
+        pattern that was compiled in an environment of one endianness is run in
+        an environment with the other endianness. This is the error  that  PCRE
+        gives when the magic number is not present.
+          PCRE_ERROR_UNKNOWN_OPCODE (-5)
+        While running the pattern match, an unknown item was encountered in the
+        compiled pattern. This error could be caused by a bug  in  PCRE  or  by
+        overwriting of the compiled pattern.
+          PCRE_ERROR_NOMEMORY       (-6)
+        If  a  pattern contains back references, but the ovector that is passed
+        to pcre_exec() is not big enough to remember the referenced substrings,
+        PCRE  gets  a  block of memory at the start of matching to use for this
+        purpose. If the call via pcre_malloc() fails, this error is given.  The
+        memory is automatically freed at the end of matching.
+          PCRE_ERROR_NOSUBSTRING    (-7)
+        This  error is used by the pcre_copy_substring(), pcre_get_substring(),
+        and  pcre_get_substring_list()  functions  (see  below).  It  is  never
+        returned by pcre_exec().
+          PCRE_ERROR_MATCHLIMIT     (-8)
+        The  backtracking  limit,  as  specified  by the match_limit field in a
+        pcre_extra structure (or defaulted) was reached.  See  the  description
+        above.
+          PCRE_ERROR_CALLOUT        (-9)
+        This error is never generated by pcre_exec() itself. It is provided for
+        use by callout functions that want to yield a distinctive  error  code.
+        See the pcrecallout documentation for details.
+          PCRE_ERROR_BADUTF8        (-10)
+        A  string  that contains an invalid UTF-8 byte sequence was passed as a
+        subject.
+          PCRE_ERROR_BADUTF8_OFFSET (-11)
+        The UTF-8 byte sequence that was passed as a subject was valid, but the
+        value  of startoffset did not point to the beginning of a UTF-8 charac-
+        ter.
+          PCRE_ERROR_PARTIAL        (-12)
+        The subject string did not match, but it did match partially.  See  the
+        pcrepartial documentation for details of partial matching.
+          PCRE_ERROR_BADPARTIAL     (-13)
+        The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
+        items that are not supported for partial matching. See the  pcrepartial
+        documentation for details of partial matching.
+          PCRE_ERROR_INTERNAL       (-14)
+        An  unexpected  internal error has occurred. This error could be caused
+        by a bug in PCRE or by overwriting of the compiled pattern.
+          PCRE_ERROR_BADCOUNT       (-15)
+        This error is given if the value of the ovecsize argument is  negative.
+          PCRE_ERROR_RECURSIONLIMIT (-21)
+        The internal recursion limit, as specified by the match_limit_recursion
+        field in a pcre_extra structure (or defaulted)  was  reached.  See  the
+        description above.
+          PCRE_ERROR_BADNEWLINE     (-23)
- MATCHING A PATTERN
+        An invalid combination of PCRE_NEWLINE_xxx options was given.
-      int pcre_exec(const pcre *code, const pcre_extra *extra,
+        Error numbers -16 to -20 and -22 are not used by pcre_exec().
-           const char *subject, int length, int startoffset,
-           int options, int *ovector, int ovecsize);
-      The function pcre_exec() is called to match a subject string
-      against  a pre-compiled pattern, which is passed in the code
-      argument. If the pattern has been studied, the result of the
-      study should be passed in the extra argument.
-      Here is an example of a simple call to pcre_exec():
-        int rc;
-        int ovector[30];
-        rc = pcre_exec(
-          re,             /* result of pcre_compile() */
-          NULL,           /* we didn't study the pattern */
-          "some string",  /* the subject string */
-,             /* the length of the subject string */
-,              /* start at offset 0 in the subject */
-,              /* default options */
-          ovector,        /* vector for substring information */
-);            /* number of elements in the vector */
-      If the extra argument is  not  NULL,  it  must  point  to  a
-      pcre_extra  data  block.  The  pcre_study() function returns
-      such a block (when it doesn't return NULL), but you can also
-      create  one for yourself, and pass additional information in
-      it. The fields in the block are as follows:
-        unsigned long int flags;
-        void *study_data;
-        unsigned long int match_limit;
-        void *callout_data;
-      The flags field is a bitmap  that  specifies  which  of  the
-      other fields are set. The flag bits are:
-        PCRE_EXTRA_STUDY_DATA
-        PCRE_EXTRA_MATCH_LIMIT
-        PCRE_EXTRA_CALLOUT_DATA
-      Other flag bits should be set to zero. The study_data  field
-      is   set  in  the  pcre_extra  block  that  is  returned  by
-      pcre_study(), together with the appropriate  flag  bit.  You
-      should  not  set this yourself, but you can add to the block
-      by setting the other fields.
-      The match_limit field provides a means  of  preventing  PCRE
-      from  using  up a vast amount of resources when running pat-
-      terns that are not going to match, but  which  have  a  very
-      large  number  of  possibilities  in their search trees. The
-      classic example is the  use  of  nested  unlimited  repeats.
-      Internally,  PCRE  uses  a  function called match() which it
-      calls  repeatedly  (sometimes  recursively).  The  limit  is
-      imposed  on the number of times this function is called dur-
-      ing a match, which has the effect of limiting the amount  of
-      recursion and backtracking that can take place. For patterns
-      that are not anchored, the count starts from zero  for  each
-      position in the subject string.
-      The default limit for the library can be set  when  PCRE  is
-      built;  the default default is 10 million, which handles all
-      but the most extreme cases. You can reduce  the  default  by
-      suppling  pcre_exec()  with  a  pcre_extra  block  in  which
-      match_limit   is   set   to    a    smaller    value,    and
-      PCRE_EXTRA_MATCH_LIMIT  is  set  in  the flags field. If the
-      limit      is      exceeded,       pcre_exec()       returns
-      PCRE_ERROR_MATCHLIMIT.
-      The pcre_callout field is used in conjunction with the "cal-
-      lout"  feature,  which is described in the pcrecallout docu-
-      mentation.
-      The PCRE_ANCHORED option can be passed in the options  argu-
-      ment,   whose   unused   bits  must  be  zero.  This  limits
-      pcre_exec() to matching at the first matching position. How-
-      ever,  if  a  pattern  was  compiled  with PCRE_ANCHORED, or
-      turned out to be anchored by virtue of its contents, it can-
-      not be made unachored at matching time.
-      There are also three further options that can be set only at
-      matching time:
-        PCRE_NOTBOL
-      The first character of the string is not the beginning of  a
-      line,  so  the  circumflex  metacharacter  should  not match
-      before it. Setting this without PCRE_MULTILINE  (at  compile
-      time) causes circumflex never to match.
-        PCRE_NOTEOL
-      The end of the string is not the end of a line, so the  dol-
-      lar  metacharacter should not match it nor (except in multi-
-      line mode) a newline immediately  before  it.  Setting  this
-      without PCRE_MULTILINE (at compile time) causes dollar never
-      to match.
-        PCRE_NOTEMPTY
-      An empty string is not considered to be  a  valid  match  if
-      this  option  is  set. If there are alternatives in the pat-
-      tern, they are tried. If  all  the  alternatives  match  the
-      empty  string,  the  entire match fails. For example, if the
-      pattern
-        a?b?
-      is applied to a string not beginning with  "a"  or  "b",  it
-      matches  the  empty string at the start of the subject. With
-      PCRE_NOTEMPTY set, this match is not valid, so PCRE searches
-      further into the string for occurrences of "a" or "b".
-      Perl has no direct equivalent of PCRE_NOTEMPTY, but it  does
-      make  a  special case of a pattern match of the empty string
-      within its split() function, and when using the /g modifier.
-      It  is possible to emulate Perl's behaviour after matching a
-      null string by first trying the  match  again  at  the  same
-      offset  with  PCRE_NOTEMPTY  set,  and then if that fails by
-      advancing the starting offset  (see  below)  and  trying  an
-      ordinary match again.
-      The subject string is passed to pcre_exec() as a pointer  in
-      subject,  a length in length, and a starting offset in star-
-      toffset. Unlike the pattern string, the subject may  contain
-      binary  zero  bytes.  When  the starting offset is zero, the
-      search for a match starts at the beginning of  the  subject,
-      and this is by far the most common case.
-      If the pattern was compiled with the PCRE_UTF8  option,  the
-      subject  must  be  a sequence of bytes that is a valid UTF-8
-      string.  If  an  invalid  UTF-8  string  is  passed,  PCRE's
-      behaviour is not defined.
-      A non-zero starting offset  is  useful  when  searching  for
-      another  match  in  the  same subject by calling pcre_exec()
-      again after a previous success.  Setting startoffset differs
-      from  just  passing  over  a  shortened  string  and setting
-      PCRE_NOTBOL in the case of a pattern that  begins  with  any
-      kind of lookbehind. For example, consider the pattern
-        \Biss\B
-      which finds occurrences of "iss" in the middle of words. (\B
-      matches only if the current position in the subject is not a
-      word boundary.) When applied to the string "Mississipi"  the
-      first  call  to  pcre_exec()  finds the first occurrence. If
-      pcre_exec() is called again with just the remainder  of  the
-      subject,  namely  "issipi", it does not match, because \B is
-      always false at the start of the subject, which is deemed to
-      be  a  word  boundary. However, if pcre_exec() is passed the
-      entire string again, but with startoffset set to 4, it finds
-      the  second  occurrence  of "iss" because it is able to look
-      behind the starting point to discover that it is preceded by
-      a letter.
-      If a non-zero starting offset is passed when the pattern  is
-      anchored, one attempt to match at the given offset is tried.
-      This can only succeed if the pattern does  not  require  the
-      match to be at the start of the subject.
-      In general, a pattern matches a certain portion of the  sub-
-      ject,  and  in addition, further substrings from the subject
-      may be picked out by parts of  the  pattern.  Following  the
-      usage  in  Jeffrey Friedl's book, this is called "capturing"
-      in what follows, and the phrase  "capturing  subpattern"  is
-      used for a fragment of a pattern that picks out a substring.
-      PCRE supports several other kinds of  parenthesized  subpat-
-      tern that do not cause substrings to be captured.
-      Captured substrings are returned to the caller via a  vector
-      of  integer  offsets whose address is passed in ovector. The
-      number of elements in the vector is passed in ovecsize.  The
-      first two-thirds of the vector is used to pass back captured
-      substrings, each substring using a  pair  of  integers.  The
-      remaining  third  of  the  vector  is  used  as workspace by
-      pcre_exec() while matching capturing subpatterns, and is not
-      available for passing back information. The length passed in
-      ovecsize should always be a multiple of three. If it is not,
-      it is rounded down.
-      When a match has been successful, information about captured
-      substrings is returned in pairs of integers, starting at the
-      beginning of ovector, and continuing up to two-thirds of its
-      length  at  the  most. The first element of a pair is set to
-      the offset of the first character in a  substring,  and  the
-      second is set to the offset of the first character after the
-      end of a substring. The first  pair,  ovector[0]  and  ovec-
-      tor[1],  identify  the portion of the subject string matched
-      by the entire pattern. The next pair is used for  the  first
-      capturing  subpattern,  and  so  on.  The  value returned by
-      pcre_exec() is the number of pairs that have  been  set.  If
-      there  are no capturing subpatterns, the return value from a
-      successful match is 1, indicating that just the  first  pair
-      of offsets has been set.
-      Some convenience functions are provided for  extracting  the
-      captured substrings as separate strings. These are described
-      in the following section.
-      It is possible for an capturing  subpattern  number  n+1  to
-      match  some  part  of  the subject when subpattern n has not
-      been used at all.  For  example,  if  the  string  "abc"  is
-      matched  against the pattern (a|(z))(bc) subpatterns 1 and 3
-      are matched, but 2 is not. When this  happens,  both  offset
-      values corresponding to the unused subpattern are set to -1.
-      If a capturing subpattern is matched repeatedly, it  is  the
-      last  portion  of  the  string  that  it  matched  that gets
-      returned.
-      If the vector is too small to hold  all  the  captured  sub-
-      strings,  it is used as far as possible (up to two-thirds of
-      its length), and the function returns a value  of  zero.  In
-      particular,  if  the  substring offsets are not of interest,
-      pcre_exec() may be called with ovector passed  as  NULL  and
-      ovecsize  as  zero.  However,  if  the pattern contains back
-      references and the ovector isn't big enough to remember  the
-      related  substrings,  PCRE  has to get additional memory for
-      use during matching. Thus it is usually advisable to  supply
-      an ovector.
-      Note that pcre_info() can be used to find out how many  cap-
-      turing  subpatterns  there  are  in  a compiled pattern. The
-      smallest size for ovector that will  allow  for  n  captured
-      substrings,  in  addition  to  the  offsets of the substring
-      matched by the whole pattern, is (n+1)*3.
-      If pcre_exec() fails, it returns a negative number. The fol-
-      lowing are defined in the header file:
-        PCRE_ERROR_NOMATCH        (-1)
-      The subject string did not match the pattern.
-        PCRE_ERROR_NULL           (-2)
-      Either code or subject was passed as NULL,  or  ovector  was
-      NULL and ovecsize was not zero.
-        PCRE_ERROR_BADOPTION      (-3)
-      An unrecognized bit was set in the options argument.
-        PCRE_ERROR_BADMAGIC       (-4)
-      PCRE stores a 4-byte "magic number" at the start of the com-
-      piled  code,  to  catch  the  case  when it is passed a junk
-      pointer. This is the error it gives when  the  magic  number
-      isn't present.
-        PCRE_ERROR_UNKNOWN_NODE   (-5)
-      While running the pattern match, an unknown item was encoun-
-      tered in the compiled pattern. This error could be caused by
-      a bug in PCRE or by overwriting of the compiled pattern.
-        PCRE_ERROR_NOMEMORY       (-6)
-      If a pattern contains back references, but the ovector  that
-      is  passed  to pcre_exec() is not big enough to remember the
-      referenced substrings, PCRE gets a block of  memory  at  the
-      start  of  matching to use for this purpose. If the call via
-      pcre_malloc() fails, this error  is  given.  The  memory  is
-      freed at the end of matching.
-        PCRE_ERROR_NOSUBSTRING    (-7)
-      This   error   is   used   by   the   pcre_copy_substring(),
-      pcre_get_substring(),  and  pcre_get_substring_list()  func-
-      tions (see below). It is never returned by pcre_exec().
-        PCRE_ERROR_MATCHLIMIT     (-8)
-      The recursion and backtracking limit, as  specified  by  the
-      match_limit  field  in a pcre_extra structure (or defaulted)
-      was reached. See the description above.
-        PCRE_ERROR_CALLOUT        (-9)
-      This error is never generated by pcre_exec() itself.  It  is
-      provided  for  use by callout functions that want to yield a
-      distinctive error code. See  the  pcrecallout  documentation
-      for details.
  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
-      int pcre_copy_substring(const char *subject, int *ovector,
+        int pcre_copy_substring(const char *subject, int *ovector,
-           int stringcount, int stringnumber, char *buffer,
+             int stringcount, int stringnumber, char *buffer,
-           int buffersize);
+             int buffersize);
-      int pcre_get_substring(const char *subject, int *ovector,
+        int pcre_get_substring(const char *subject, int *ovector,
-           int stringcount, int stringnumber,
+             int stringcount, int stringnumber,
-           const char **stringptr);
+             const char **stringptr);
-      int pcre_get_substring_list(const char *subject,
+        int pcre_get_substring_list(const char *subject,
-           int *ovector, int stringcount, const char ***listptr);
+             int *ovector, int stringcount, const char ***listptr);
-      Captured substrings can be accessed directly  by  using  the
+        Captured  substrings  can  be  accessed  directly  by using the offsets
-      offsets returned by pcre_exec() in ovector. For convenience,
+        returned by pcre_exec() in  ovector.  For  convenience,  the  functions
-      the functions  pcre_copy_substring(),  pcre_get_substring(),
+        pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
-      and  pcre_get_substring_list()  are  provided for extracting
+        string_list() are provided for extracting captured substrings  as  new,
-      captured  substrings  as  new,   separate,   zero-terminated
+        separate,  zero-terminated strings. These functions identify substrings
-      strings.  These functions identify substrings by number. The
+        by number. The next section describes functions  for  extracting  named
-      next section describes functions for extracting  named  sub-
+        substrings.
-      strings.   A  substring  that  contains  a  binary  zero  is
-      correctly extracted and has a further zero added on the end,
+        A  substring that contains a binary zero is correctly extracted and has
-      but the result is not, of course, a C string.
+        a further zero added on the end, but the result is not, of course, a  C
+        string.   However,  you  can  process such a string by referring to the
-      The first three arguments are the  same  for  all  three  of
+        length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
-      these  functions:   subject  is the subject string which has
+        string().  Unfortunately, the interface to pcre_get_substring_list() is
-      just been successfully matched, ovector is a pointer to  the
+        not adequate for handling strings containing binary zeros, because  the
-      vector  of  integer  offsets that was passed to pcre_exec(),
+        end of the final string is not independently indicated.
-      and stringcount is the number of substrings that  were  cap-
-      tured by the match, including the substring that matched the
+        The  first  three  arguments  are the same for all three of these func-
-      entire regular expression. This is  the  value  returned  by
+        tions: subject is the subject string that has  just  been  successfully
-      pcre_exec  if  it  is  greater  than  zero.  If  pcre_exec()
+        matched, ovector is a pointer to the vector of integer offsets that was
-      returned zero, indicating that it ran out of space in  ovec-
+        passed to pcre_exec(), and stringcount is the number of substrings that
-      tor,  the  value passed as stringcount should be the size of
+        were  captured  by  the match, including the substring that matched the
-      the vector divided by three.
+        entire regular expression. This is the value returned by pcre_exec() if
+        it  is greater than zero. If pcre_exec() returned zero, indicating that
-      The functions pcre_copy_substring() and pcre_get_substring()
+        it ran out of space in ovector, the value passed as stringcount  should
-      extract a single substring, whose number is given as string-
+        be the number of elements in the vector divided by three.
-      number. A value of zero extracts the substring that  matched
-      the entire pattern, while higher values extract the captured
+        The  functions pcre_copy_substring() and pcre_get_substring() extract a
-      substrings. For pcre_copy_substring(), the string is  placed
+        single substring, whose number is given as  stringnumber.  A  value  of
-      in  buffer,  whose  length is given by buffersize, while for
+        zero  extracts  the  substring that matched the entire pattern, whereas
-      pcre_get_substring() a new block of memory is  obtained  via
+        higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
-      pcre_malloc,  and its address is returned via stringptr. The
+        string(),  the  string  is  placed  in buffer, whose length is given by
-      yield of the function is  the  length  of  the  string,  not
+        buffersize, while for pcre_get_substring() a new  block  of  memory  is
-      including the terminating zero, or one of
+        obtained  via  pcre_malloc,  and its address is returned via stringptr.
+        The yield of the function is the length of the  string,  not  including
-        PCRE_ERROR_NOMEMORY       (-6)
+        the terminating zero, or one of these error codes:
-      The buffer was too small for pcre_copy_substring(),  or  the
+          PCRE_ERROR_NOMEMORY       (-6)
-      attempt to get memory failed for pcre_get_substring().
+        The  buffer  was too small for pcre_copy_substring(), or the attempt to
-        PCRE_ERROR_NOSUBSTRING    (-7)
+        get memory failed for pcre_get_substring().
-      There is no substring whose number is stringnumber.
+          PCRE_ERROR_NOSUBSTRING    (-7)
-      The pcre_get_substring_list() function extracts  all  avail-
+        There is no substring whose number is stringnumber.
-      able  substrings  and builds a list of pointers to them. All
-      this is done in a single block of memory which  is  obtained
+        The pcre_get_substring_list()  function  extracts  all  available  sub-
-      via pcre_malloc. The address of the memory block is returned
+        strings  and  builds  a list of pointers to them. All this is done in a
-      via listptr, which is also the start of the list  of  string
+        single block of memory that is obtained via pcre_malloc. The address of
-      pointers.  The  end of the list is marked by a NULL pointer.
+        the  memory  block  is returned via listptr, which is also the start of
-      The yield of the function is zero if all went well, or
+        the list of string pointers. The end of the list is marked  by  a  NULL
+        pointer.  The  yield  of  the function is zero if all went well, or the
-        PCRE_ERROR_NOMEMORY       (-6)
+        error code
-      if the attempt to get the memory block failed.
+          PCRE_ERROR_NOMEMORY       (-6)
-      When any of these functions encounter a  substring  that  is
+        if the attempt to get the memory block failed.
-      unset, which can happen when capturing subpattern number n+1
-      matches some part of the subject, but subpattern n  has  not
+        When any of these functions encounter a substring that is unset,  which
-      been  used  at all, they return an empty string. This can be
+        can  happen  when  capturing subpattern number n+1 matches some part of
-      distinguished  from  a  genuine  zero-length  substring   by
+        the subject, but subpattern n has not been used at all, they return  an
-      inspecting the appropriate offset in ovector, which is nega-
+        empty string. This can be distinguished from a genuine zero-length sub-
-      tive for unset substrings.
+        string by inspecting the appropriate offset in ovector, which is  nega-
+        tive for unset substrings.
-      The  two  convenience  functions  pcre_free_substring()  and
-      pcre_free_substring_list()  can  be  used to free the memory
+        The  two convenience functions pcre_free_substring() and pcre_free_sub-
-      returned by  a  previous  call  of  pcre_get_substring()  or
+        string_list() can be used to free the memory  returned  by  a  previous
-      pcre_get_substring_list(),  respectively.  They  do  nothing
+        call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
-      more than call the function pointed to by  pcre_free,  which
+        tively. They do nothing more than  call  the  function  pointed  to  by
-      of  course  could  be called directly from a C program. How-
+        pcre_free,  which  of course could be called directly from a C program.
-      ever, PCRE is used in some situations where it is linked via
+        However, PCRE is used in some situations where it is linked via a  spe-
-      a  special  interface  to another programming language which
+        cial   interface  to  another  programming  language  that  cannot  use
-      cannot use pcre_free directly; it is for  these  cases  that
+        pcre_free directly; it is for these cases that the functions  are  pro-
-      the functions are provided.
+        vided.
  EXTRACTING CAPTURED SUBSTRINGS BY NAME
-      int pcre_copy_named_substring(const pcre *code,
+        int pcre_get_stringnumber(const pcre *code,
-           const char *subject, int *ovector,
+             const char *name);
-           int stringcount, const char *stringname,
-           char *buffer, int buffersize);
+        int pcre_copy_named_substring(const pcre *code,
+             const char *subject, int *ovector,
-      int pcre_get_stringnumber(const pcre *code,
+             int stringcount, const char *stringname,
-           const char *name);
+             char *buffer, int buffersize);
-      int pcre_get_named_substring(const pcre *code,
+        int pcre_get_named_substring(const pcre *code,
-           const char *subject, int *ovector,
+             const char *subject, int *ovector,
-           int stringcount, const char *stringname,
+             int stringcount, const char *stringname,
-           const char **stringptr);
+             const char **stringptr);
-      To extract a substring by name, you first have to find asso-
+        To  extract a substring by name, you first have to find associated num-
-      ciated    number.    This    can    be   done   by   calling
+        ber.  For example, for this pattern
-      pcre_get_stringnumber(). The first argument is the  compiled
-      pattern,  and  the second is the name. For example, for this
+          (a+)b(?<xxx>\d+)...
-      pattern
+        the number of the subpattern called "xxx" is 2. If the name is known to
-        ab(?<xxx>\d+)...
+        be unique (PCRE_DUPNAMES was not set), you can find the number from the
+        name by calling pcre_get_stringnumber(). The first argument is the com-
-      the number of the subpattern called "xxx" is  1.  Given  the
+        piled pattern, and the second is the name. The yield of the function is
-      number,  you can then extract the substring directly, or use
+        the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
-      one of the functions described in the previous section.  For
+        subpattern of that name.
-      convenience,  there are also two functions that do the whole
-      job.
+        Given the number, you can extract the substring directly, or use one of
+        the functions described in the previous section. For convenience, there
-      Most of the  arguments  of  pcre_copy_named_substring()  and
+        are also two functions that do the whole job.
-      pcre_get_named_substring()  are  the  same  as those for the
-      functions that  extract  by  number,  and  so  are  not  re-
+        Most    of    the    arguments   of   pcre_copy_named_substring()   and
-      described here. There are just two differences.
+        pcre_get_named_substring() are the same  as  those  for  the  similarly
+        named  functions  that extract by number. As these are described in the
-      First, instead of a substring number, a  substring  name  is
+        previous section, they are not re-described here. There  are  just  two
-      given.  Second,  there  is  an  extra argument, given at the
+        differences:
-      start, which is a pointer to the compiled pattern.  This  is
-      needed  in order to gain access to the name-to-number trans-
+        First,  instead  of a substring number, a substring name is given. Sec-
-      lation table.
+        ond, there is an extra argument, given at the start, which is a pointer
+        to  the compiled pattern. This is needed in order to gain access to the
-      These functions  call  pcre_get_stringnumber(),  and  if  it
+        name-to-number translation table.
-      succeeds,    they   then   call   pcre_copy_substring()   or
-      pcre_get_substring(), as appropriate.
+        These functions call pcre_get_stringnumber(), and if it succeeds,  they
+        then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
+        ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
+        behaviour may not be what you want (see the next section).
+ DUPLICATE SUBPATTERN NAMES
+        int pcre_get_stringtable_entries(const pcre *code,
+             const char *name, char **first, char **last);
+        When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
+        subpatterns are not required to  be  unique.  Normally,  patterns  with
+        duplicate  names  are such that in any one match, only one of the named
+        subpatterns participates. An example is shown in the pcrepattern  docu-
+        mentation.
+        When    duplicates   are   present,   pcre_copy_named_substring()   and
+        pcre_get_named_substring() return the first substring corresponding  to
+        the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
+        (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
+        function  returns one of the numbers that are associated with the name,
+        but it is not defined which it is.
+        If you want to get full details of all captured substrings for a  given
+        name,  you  must  use  the pcre_get_stringtable_entries() function. The
+        first argument is the compiled pattern, and the second is the name. The
+        third  and  fourth  are  pointers to variables which are updated by the
+        function. After it has run, they point to the first and last entries in
+        the  name-to-number  table  for  the  given  name.  The function itself
+        returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
+        there  are none. The format of the table is described above in the sec-
+        tion entitled Information about a  pattern.   Given  all  the  relevant
+        entries  for the name, you can extract each of their numbers, and hence
+        the captured data, if any.
+ FINDING ALL POSSIBLE MATCHES
+        The traditional matching function uses a  similar  algorithm  to  Perl,
+        which stops when it finds the first match, starting at a given point in
+        the subject. If you want to find all possible matches, or  the  longest
+        possible  match,  consider using the alternative matching function (see
+        below) instead. If you cannot use the alternative function,  but  still
+        need  to  find all possible matches, you can kludge it up by making use
+        of the callout facility, which is described in the pcrecallout documen-
+        tation.
+        What you have to do is to insert a callout right at the end of the pat-
+        tern.  When your callout function is called, extract and save the  cur-
+        rent  matched  substring.  Then  return  1, which forces pcre_exec() to
+        backtrack and try other alternatives. Ultimately, when it runs  out  of
+        matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
+ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
+        int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
+             const char *subject, int length, int startoffset,
+             int options, int *ovector, int ovecsize,
+             int *workspace, int wscount);
+        The  function  pcre_dfa_exec()  is  called  to  match  a subject string
+        against a compiled pattern, using a matching algorithm that  scans  the
+        subject  string  just  once, and does not backtrack. This has different
+        characteristics to the normal algorithm, and  is  not  compatible  with
+        Perl.  Some  of the features of PCRE patterns are not supported. Never-
+        theless, there are times when this kind of matching can be useful.  For
+        a discussion of the two matching algorithms, see the pcrematching docu-
+        mentation.
+        The arguments for the pcre_dfa_exec() function  are  the  same  as  for
+        pcre_exec(), plus two extras. The ovector argument is used in a differ-
+        ent way, and this is described below. The other  common  arguments  are
+        used  in  the  same way as for pcre_exec(), so their description is not
+        repeated here.
+        The two additional arguments provide workspace for  the  function.  The
+        workspace  vector  should  contain at least 20 elements. It is used for
+        keeping  track  of  multiple  paths  through  the  pattern  tree.  More
+        workspace  will  be  needed for patterns and subjects where there are a
+        lot of potential matches.
+        Here is an example of a simple call to pcre_dfa_exec():
+          int rc;
+          int ovector[10];
+          int wspace[20];
+          rc = pcre_dfa_exec(
+            re,             /* result of pcre_compile() */
+            NULL,           /* we didn't study the pattern */
+            "some string",  /* the subject string */
+,             /* the length of the subject string */
+,              /* start at offset 0 in the subject */
+,              /* default options */
+            ovector,        /* vector of integers for substring information */
+,             /* number of elements (NOT size in bytes) */
+            wspace,         /* working space vector */
+);            /* number of elements (NOT size in bytes) */
+    Option bits for pcre_dfa_exec()
+        The unused bits of the options argument  for  pcre_dfa_exec()  must  be
+        zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-
+        LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,
+        PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
+        three of these are the same as for pcre_exec(), so their description is
+        not repeated here.
+          PCRE_PARTIAL
+        This  has  the  same general effect as it does for pcre_exec(), but the
+        details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for
+        pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into
+        PCRE_ERROR_PARTIAL if the end of the subject  is  reached,  there  have
+        been no complete matches, but there is still at least one matching pos-
+        sibility. The portion of the string that provided the partial match  is
+        set as the first matching string.
+          PCRE_DFA_SHORTEST
+        Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
+        stop as soon as it has found one match. Because of the way the alterna-
+        tive  algorithm  works, this is necessarily the shortest possible match
+        at the first possible matching point in the subject string.
+          PCRE_DFA_RESTART
+        When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and
+        returns  a  partial  match, it is possible to call it again, with addi-
+        tional subject characters, and have it continue with  the  same  match.
+        The  PCRE_DFA_RESTART  option requests this action; when it is set, the
+        workspace and wscount options must reference the same vector as  before
+        because  data  about  the  match so far is left in them after a partial
+        match. There is more discussion of this  facility  in  the  pcrepartial
+        documentation.
+    Successful returns from pcre_dfa_exec()
+        When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
+        string in the subject. Note, however, that all the matches from one run
+        of  the  function  start  at the same point in the subject. The shorter
+        matches are all initial substrings of the longer matches. For  example,
+        if the pattern
+          <.*>
+        is matched against the string
+          This is <something> <something else> <something further> no more
+        the three matched strings are
+          <something>
+          <something> <something else>
+          <something> <something else> <something further>
+        On  success,  the  yield of the function is a number greater than zero,
+        which is the number of matched substrings.  The  substrings  themselves
+        are  returned  in  ovector. Each string uses two elements; the first is
+        the offset to the start, and the second is the offset to  the  end.  In
+        fact,  all  the  strings  have the same start offset. (Space could have
+        been saved by giving this only once, but it was decided to retain  some
+        compatibility  with  the  way pcre_exec() returns data, even though the
+        meaning of the strings is different.)
+        The strings are returned in reverse order of length; that is, the long-
+        est  matching  string is given first. If there were too many matches to
+        fit into ovector, the yield of the function is zero, and the vector  is
+        filled with the longest matches.
+    Error returns from pcre_dfa_exec()
+        The  pcre_dfa_exec()  function returns a negative number when it fails.
+        Many of the errors are the same  as  for  pcre_exec(),  and  these  are
+        described  above.   There are in addition the following errors that are
+        specific to pcre_dfa_exec():
+          PCRE_ERROR_DFA_UITEM      (-16)
+        This return is given if pcre_dfa_exec() encounters an item in the  pat-
+        tern  that  it  does not support, for instance, the use of \C or a back
+        reference.
+          PCRE_ERROR_DFA_UCOND      (-17)
+        This return is given if pcre_dfa_exec()  encounters  a  condition  item
+        that  uses  a back reference for the condition, or a test for recursion
+        in a specific group. These are not supported.
+          PCRE_ERROR_DFA_UMLIMIT    (-18)
+        This return is given if pcre_dfa_exec() is called with an  extra  block
+        that contains a setting of the match_limit field. This is not supported
+        (it is meaningless).
+          PCRE_ERROR_DFA_WSSIZE     (-19)
+        This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
+        workspace vector.
+          PCRE_ERROR_DFA_RECURSE    (-20)
+        When  a  recursive subpattern is processed, the matching function calls
+        itself recursively, using private vectors for  ovector  and  workspace.
+        This  error  is  given  if  the output vector is not large enough. This
+        should be extremely rare, as a vector of size 1000 is used.
+ SEE ALSO
+        pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
+        tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
+ AUTHOR
+        Philip Hazel
+        University Computing Service
+        Cambridge CB2 3QH, England.
+ REVISION
+        Last updated: 12 April 2008
+        Copyright (c) 1997-2008 University of Cambridge.
+ ------------------------------------------------------------------------------
+ PCRECALLOUT(3)                                                  PCRECALLOUT(3)
- Last updated: 03 February 2003
- Copyright (c) 1997-2003 University of Cambridge.
- -----------------------------------------------------------------------------
  NAME
-      PCRE - Perl-compatible regular expressions
+        PCRE - Perl-compatible regular expressions
  PCRE CALLOUTS
-      int (*pcre_callout)(pcre_callout_block *);
+        int (*pcre_callout)(pcre_callout_block *);
-      PCRE provides a feature called "callout", which is  a  means
-      of  temporarily passing control to the caller of PCRE in the
-      middle of pattern matching. The caller of PCRE  provides  an
-      external  function  by putting its entry point in the global
-      variable pcre_callout. By default,  this  variable  contains
-      NULL, which disables all calling out.
-      Within a regular expression, (?C) indicates  the  points  at
-      which  the external function is to be called. Different cal-
-      lout points can be identified by putting a number less  than
- after  the  letter  C.  The default value is zero.  For
-      example, this pattern has two callout points:
-        (?C1)9abc(?C2)def
-      During matching, when PCRE  reaches  a  callout  point  (and
-      pcre_callout  is  set), the external function is called. Its
-      only argument is a pointer to  a  pcre_callout  block.  This
-      contains the following variables:
-        int          version;
-        int          callout_number;
-        int         *offset_vector;
-        const char  *subject;
-        int          subject_length;
-        int          start_match;
-        int          current_position;
-        int          capture_top;
-        int          capture_last;
-        void        *callout_data;
-      The version field  is  an  integer  containing  the  version
-      number of the block format. The current version is zero. The
-      version number may change in future if additional fields are
-      added,  but  the  intention  is  never  to remove any of the
-      existing fields.
-      The callout_number field contains the number of the callout,
-      as compiled into the pattern (that is, the number after ?C).
-      The offset_vector field  is  a  pointer  to  the  vector  of
-      offsets  that  was  passed by the caller to pcre_exec(). The
-      contents can be inspected in  order  to  extract  substrings
-      that  have  been  matched  so  far,  in  the same way as for
-      extracting substrings after a match has completed.
-      The subject and subject_length  fields  contain  copies  the
-      values that were passed to pcre_exec().
-      The start_match field contains the offset within the subject
-      at  which  the current match attempt started. If the pattern
-      is not anchored, the callout function may be called  several
-      times for different starting points.
-      The current_position field contains the  offset  within  the
-      subject of the current match pointer.
-      The capture_top field contains the  number  of  the  highest
-      captured substring so far.
-      The capture_last field  contains  the  number  of  the  most
-      recently captured substring.
-      The callout_data field contains a value that  is  passed  to
-      pcre_exec()  by  the  caller  specifically so that it can be
-      passed back in callouts. It is passed  in  the  pcre_callout
-      field  of the pcre_extra data structure. If no such data was
-      passed, the value of callout_data in a pcre_callout block is
-      NULL.  There is a description of the pcre_extra structure in
-      the pcreapi documentation.
+        PCRE provides a feature called "callout", which is a means of temporar-
+        ily passing control to the caller of PCRE  in  the  middle  of  pattern
+        matching.  The  caller of PCRE provides an external function by putting
+        its entry point in the global variable pcre_callout. By  default,  this
+        variable contains NULL, which disables all calling out.
+        Within  a  regular  expression,  (?C) indicates the points at which the
+        external function is to be called.  Different  callout  points  can  be
+        identified  by  putting  a number less than 256 after the letter C. The
+        default value is zero.  For  example,  this  pattern  has  two  callout
+        points:
+          (?C1)abc(?C2)def
+        If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
+        called, PCRE automatically  inserts  callouts,  all  with  number  255,
+        before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is
+        used with the pattern
+          A(\d{2}|--)
+        it is processed as if it were
+        (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255)
+        Notice that there is a callout before and after  each  parenthesis  and
+        alternation  bar.  Automatic  callouts  can  be  used  for tracking the
+        progress of pattern matching. The pcretest command has an  option  that
+        sets  automatic callouts; when it is used, the output indicates how the
+        pattern is matched. This is useful information when you are  trying  to
+        optimize the performance of a particular pattern.
+ MISSING CALLOUTS
+        You  should  be  aware  that,  because of optimizations in the way PCRE
+        matches patterns, callouts sometimes do not happen. For example, if the
+        pattern is
+          ab(?C4)cd
+        PCRE knows that any matching string must contain the letter "d". If the
+        subject string is "abyz", the lack of "d" means that  matching  doesn't
+        ever  start,  and  the  callout is never reached. However, with "abyd",
+        though the result is still no match, the callout is obeyed.
+ THE CALLOUT INTERFACE
+        During matching, when PCRE reaches a callout point, the external  func-
+        tion  defined by pcre_callout is called (if it is set). This applies to
+        both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The
+        only  argument  to  the callout function is a pointer to a pcre_callout
+        block. This structure contains the following fields:
+          int          version;
+          int          callout_number;
+          int         *offset_vector;
+          const char  *subject;
+          int          subject_length;
+          int          start_match;
+          int          current_position;
+          int          capture_top;
+          int          capture_last;
+          void        *callout_data;
+          int          pattern_position;
+          int          next_item_length;
+        The version field is an integer containing the version  number  of  the
+        block  format. The initial version was 0; the current version is 1. The
+        version number will change again in future  if  additional  fields  are
+        added, but the intention is never to remove any of the existing fields.
+        The callout_number field contains the number of the  callout,  as  com-
+        piled  into  the pattern (that is, the number after ?C for manual call-
+        outs, and 255 for automatically generated callouts).
+        The offset_vector field is a pointer to the vector of offsets that  was
+        passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
+        pcre_exec() is used, the contents can be inspected in order to  extract
+        substrings  that  have  been  matched  so  far,  in the same way as for
+        extracting substrings after a match has completed. For  pcre_dfa_exec()
+        this field is not useful.
+        The subject and subject_length fields contain copies of the values that
+        were passed to pcre_exec().
+        The start_match field normally contains the offset within  the  subject
+        at  which  the  current  match  attempt started. However, if the escape
+        sequence \K has been encountered, this value is changed to reflect  the
+        modified  starting  point.  If the pattern is not anchored, the callout
+        function may be called several times from the same point in the pattern
+        for different starting points in the subject.
+        The  current_position  field  contains the offset within the subject of
+        the current match pointer.
+        When the pcre_exec() function is used, the capture_top  field  contains
+        one  more than the number of the highest numbered captured substring so
+        far. If no substrings have been captured, the value of  capture_top  is
+        one.  This  is always the case when pcre_dfa_exec() is used, because it
+        does not support captured substrings.
+        The capture_last field contains the number of the  most  recently  cap-
+        tured  substring. If no substrings have been captured, its value is -1.
+        This is always the case when pcre_dfa_exec() is used.
+        The callout_data field contains a value that is passed  to  pcre_exec()
+        or  pcre_dfa_exec() specifically so that it can be passed back in call-
+        outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
+        structure.  If  no such data was passed, the value of callout_data in a
+        pcre_callout block is NULL. There is a description  of  the  pcre_extra
+        structure in the pcreapi documentation.
+        The  pattern_position field is present from version 1 of the pcre_call-
+        out structure. It contains the offset to the next item to be matched in
+        the pattern string.
+        The  next_item_length field is present from version 1 of the pcre_call-
+        out structure. It contains the length of the next item to be matched in
+        the  pattern  string. When the callout immediately precedes an alterna-
+        tion bar, a closing parenthesis, or the end of the pattern, the  length
+        is  zero.  When the callout precedes an opening parenthesis, the length
+        is that of the entire subpattern.
+        The pattern_position and next_item_length fields are intended  to  help
+        in  distinguishing between different automatic callouts, which all have
+        the same callout number. However, they are set for all callouts.
  RETURN VALUES
-      The callout function returns an integer.  If  the  value  is
+        The external callout function returns an integer to PCRE. If the  value
-      zero,  matching  proceeds as normal. If the value is greater
+        is  zero,  matching  proceeds  as  normal. If the value is greater than
-      than zero, matching fails at the current  point,  but  back-
+        zero, matching fails at the current point, but  the  testing  of  other
-      tracking  to test other possibilities goes ahead, just as if
+        matching possibilities goes ahead, just as if a lookahead assertion had
-      a lookahead assertion had failed. If the value is less  than
+        failed. If the value is less than zero, the  match  is  abandoned,  and
-      zero,  the  match  is abandoned, and pcre_exec() returns the
+        pcre_exec() (or pcre_dfa_exec()) returns the negative value.
-      value.
+        Negative   values   should   normally   be   chosen  from  the  set  of
-      Negative values should normally be chosen from  the  set  of
+        PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
-      PCRE_ERROR_xxx  values.  In  particular,  PCRE_ERROR_NOMATCH
+        dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
-      forces a standard "no  match"  failure.   The  error  number
+        reserved for use by callout functions; it will never be  used  by  PCRE
-      PCRE_ERROR_CALLOUT is reserved for use by callout functions;
+        itself.
-      it will never be used by PCRE itself.
+ AUTHOR
+        Philip Hazel
+        University Computing Service
+        Cambridge CB2 3QH, England.
+ REVISION
+        Last updated: 29 May 2007
+        Copyright (c) 1997-2007 University of Cambridge.
+ ------------------------------------------------------------------------------
+ PCRECOMPAT(3)                                                    PCRECOMPAT(3)
- Last updated: 21 January 2003
- Copyright (c) 1997-2003 University of Cambridge.
- -----------------------------------------------------------------------------
  NAME
-      PCRE - Perl-compatible regular expressions
+        PCRE - Perl-compatible regular expressions
+ DIFFERENCES BETWEEN PCRE AND PERL
- DIFFERENCES FROM PERL
+        This  document describes the differences in the ways that PCRE and Perl
+        handle regular expressions. The differences described here  are  mainly
+        with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
+        some features that are expected to be in the forthcoming Perl 5.10.
+. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
+        of  what  it does have are given in the section on UTF-8 support in the
+        main pcre page.
+. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
+        permits  them,  but they do not mean what you might think. For example,
+        (?!a){3} does not assert that the next three characters are not "a". It
+        just asserts that the next character is not "a" three times.
+.  Capturing  subpatterns  that occur inside negative lookahead asser-
+        tions are counted, but their entries in the offsets  vector  are  never
+        set.  Perl sets its numerical variables from any such patterns that are
+        matched before the assertion fails to match something (thereby succeed-
+        ing),  but  only  if the negative lookahead assertion contains just one
+        branch.
+. Though binary zero characters are supported in the  subject  string,
+        they are not allowed in a pattern string because it is passed as a nor-
+        mal C string, terminated by zero. The escape sequence \0 can be used in
+        the pattern to represent a binary zero.
+.  The  following Perl escape sequences are not supported: \l, \u, \L,
+        \U, and \N. In fact these are implemented by Perl's general string-han-
+        dling  and are not part of its pattern matching engine. If any of these
+        are encountered by PCRE, an error is generated.
+. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
+        is  built  with Unicode character property support. The properties that
+        can be tested with \p and \P are limited to the general category  prop-
+        erties  such  as  Lu and Nd, script names such as Greek or Han, and the
+        derived properties Any and L&.
+. PCRE does support the \Q...\E escape for quoting substrings. Charac-
+        ters  in  between  are  treated as literals. This is slightly different
+        from Perl in that $ and @ are  also  handled  as  literals  inside  the
+        quotes.  In Perl, they cause variable interpolation (but of course PCRE
+        does not have variables). Note the following examples:
+            Pattern            PCRE matches      Perl matches
+            \Qabc$xyz\E        abc$xyz           abc followed by the
+                                                   contents of $xyz