/[pcre]/code/tags/pcre-5.0/doc/pcre.txt

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-revision 41 by nigel,
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+revision 69 by nigel,
Sat Feb 24 21:40:18 2007 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
+ synopses of each function in the library have not been included. There are
+ separate text files for the pcregrep and pcretest commands.
+ -----------------------------------------------------------------------------
+ NAME
+      PCRE - Perl-compatible regular expressions
+ DESCRIPTION
+      The PCRE library is a set of functions that implement  regu-
+      lar  expression  pattern  matching using the same syntax and
+      semantics as Perl, with just a few differences. The  current
+      implementation  of  PCRE  (release 4.x) corresponds approxi-
+      mately with Perl 5.8, including support  for  UTF-8  encoded
+      strings.    However,  this  support  has  to  be  explicitly
+      enabled; it is not the default.
+      PCRE is written in C and released as a C library. However, a
+      number  of  people  have  written wrappers and interfaces of
+      various kinds. A C++ class is included  in  these  contribu-
+      tions,  which  can  be found in the 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 pcrepattern and pcrecompat pages.
+      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.  Documentation  about  building  PCRE for various
+      operating systems can be found in the  README  file  in  the
+      source distribution.
+ USER DOCUMENTATION
+      The user documentation for PCRE has been  split  up  into  a
+      number  of  different sections. In the "man" format, each of
+      these is a separate "man page". In the HTML format, each  is
+      a  separate  page,  linked from the index page. In the plain
+      text format, all the sections are concatenated, for ease  of
+      searching. The sections are as follows:
+        pcre              this document
+        pcreapi           details of PCRE's native API
+        pcrebuild         options for building PCRE
+        pcrecallout       details of the callout feature
+        pcrecompat        discussion of Perl compatibility
+        pcregrep          description of the pcregrep command
+        pcrepattern       syntax and semantics of supported
+                            regular expressions
+        pcreperform       discussion of performance issues
+        pcreposix         the POSIX-compatible API
+        pcresample        discussion of the sample program
+        pcretest          the pcretest testing command
+      In addition, in the "man" and HTML formats, there is a short
+      page  for  each  library function, listing its arguments and
+      results.
+ LIMITATIONS
+      There are some size limitations in PCRE but it is hoped that
+      they will never in practice be relevant.
+      The maximum length of a  compiled  pattern  is  65539  (sic)
+      bytes  if PCRE is compiled with the default internal linkage
+      size of 2. If you want to process regular  expressions  that
+      are  truly  enormous,  you can compile PCRE with an internal
+      linkage size of 3 or 4 (see the README file  in  the  source
+      distribution  and  the pcrebuild documentation for details).
+      If these cases the limit is substantially larger.   However,
+      the speed of execution will be slower.
+      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  non-capturing  subpat-
+      terns,  but  the  maximum  depth  of nesting of all kinds of
+      parenthesized subpattern, including  capturing  subpatterns,
+      assertions, and other types of subpattern, is 200.
+      The maximum length of a subject string is the largest  posi-
+      tive number that an integer variable can hold. However, PCRE
+      uses recursion to handle subpatterns and indefinite  repeti-
+      tion.  This  means  that the available stack space may limit
+      the size of a subject string that can be processed  by  cer-
+      tain patterns.
+ UTF-8 SUPPORT
+      Starting at release 3.3, PCRE has had some support for char-
+      acter  strings  encoded in the UTF-8 format. For release 4.0
+      this has been greatly extended to cover most common require-
+      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-
+      perties or the Perl escapes \p, \P, and \X.
+ AUTHOR
+      Philip Hazel <ph10@cam.ac.uk>
+      University Computing Service,
+      Cambridge CB2 3QG, England.
+      Phone: +44 1223 334714
+ Last updated: 04 February 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
+ NAME
+      PCRE - Perl-compatible regular expressions
+ PCRE BUILD-TIME OPTIONS
+      This document describes the optional features of  PCRE  that
+      can  be  selected when the library is compiled. They are all
+      selected, or deselected, by providing options to the config-
+      ure  script  which  is run before the make command. The com-
+      plete list of options  for  configure  (which  includes  the
+      standard  ones  such  as  the  selection of the installation
+      directory) can be obtained by running
+        ./configure --help
+      The following sections describe certain options whose  names
+      begin  with  --enable  or  --disable. These settings specify
+      changes to the defaults for the configure  command.  Because
+      of  the  way  that  configure  works, --enable and --disable
+      always come in pairs, so  the  complementary  option  always
+      exists  as  well, but as it specifies the default, it is not
+      described.
+ UTF-8 SUPPORT
+      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.
+ CODE VALUE OF NEWLINE
+      By default, PCRE treats character 10 (linefeed) as the  new-
+      line  character.  This  is  the  normal newline character on
+      Unix-like systems. You can compile PCRE to use character  13
+      (carriage return) instead by adding
+        --enable-newline-is-cr
+      to the configure command. For completeness there is  also  a
+      --enable-newline-is-lf  option,  which  explicitly specifies
+      linefeed as the newline character.
+ BUILDING SHARED AND STATIC LIBRARIES
+      The PCRE building process uses libtool to build both  shared
+      and  static  Unix libraries by default. You can suppress one
+      of these by adding one of
+        --disable-shared
+        --disable-static
+      to the configure command, as required.
+ POSIX MALLOC USAGE
+      When PCRE is called through the  POSIX  interface  (see  the
+      pcreposix  documentation),  additional  working  storage  is
+      required for holding the pointers  to  capturing  substrings
+      because  PCRE requires three integers per substring, whereas
+      the POSIX interface provides only  two.  If  the  number  of
+      expected  substrings  is  small,  the  wrapper function uses
+      space on the stack, because this is faster than  using  mal-
+      loc()  for  each call. The default threshold above which the
+      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.
+ LIMITING PCRE RESOURCE USAGE
+      Internally, PCRE has a  function  called  match()  which  it
+      calls  repeatedly  (possibly  recursively) when performing a
+      matching operation. By limiting the  number  of  times  this
+      function  may  be  called,  a  limit  can  be  placed on the
+      resources used by a single call to  pcre_exec().  The  limit
+      can  be  changed  at  run  time, as described in the pcreapi
+      documentation. The default is 10 million, but  this  can  be
+      changed by adding a setting such as
+        --with-match-limit=500000
+      to the configure command.
+ HANDLING VERY LARGE PATTERNS
+      Within a compiled pattern, offset values are used  to  point
+      from  one  part  to  another  (for  example, from an opening
+      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
+      sufficient  to  handle  all  but the most gigantic patterns.
+      Nevertheless, some people do want to process  enormous  pat-
+      terns,  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
+.  Using  longer  offsets  slows down the operation of PCRE
+      because it has to load additional bytes when handling them.
+      If you build PCRE with an increased link size, test  2  (and
+      test 5 if you are using UTF-8) will fail. Part of the output
+      of these tests is a representation of the compiled  pattern,
+      and this changes with the link size.
+ Last updated: 21 January 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
  NAME
-      pcre - Perl-compatible regular expressions.
+      PCRE - Perl-compatible regular expressions
+ SYNOPSIS OF PCRE API
- SYNOPSIS
       #include <pcre.h>
       pcre *pcre_compile(const char *pattern, int options,
-Line 17 
 SYNOPSIS
+Line 311 
 SYNOPSIS
            const char *subject, int length, int startoffset,
            int options, int *ovector, int ovecsize);
+      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_substring(const char *subject, int *ovector,
            int stringcount, int stringnumber,
            const char **stringptr);
-Line 28 
 SYNOPSIS
+Line 335 
 SYNOPSIS
       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, *firstcharptr);
+      int pcre_config(int what, void *where);
       char *pcre_version(void);
       void *(*pcre_malloc)(size_t);
       void (*pcre_free)(void *);
+      int (*pcre_callout)(pcre_callout_block *);
+ PCRE API
- DESCRIPTION
-      The PCRE library is a set of functions that implement  regu-
-      lar  expression  pattern  matching using the same syntax and
-      semantics as Perl  5,  with  just  a  few  differences  (see
-      below).  The  current  implementation  corresponds  to  Perl
-.005.
       PCRE has its own native API,  which  is  described  in  this
       document.  There  is  also  a  set of wrapper functions that
-      correspond to the POSIX API.  These  are  described  in  the
+      correspond to the POSIX regular expression API.   These  are
-      pcreposix documentation.
+      described in the pcreposix documentation.
       The native API function prototypes are defined in the header
       file  pcre.h,  and  on  Unix  systems  the library itself is
       called libpcre.a, so can be accessed by adding -lpcre to the
-      command for linking an application which calls it.
+      command  for  linking  an  application  which  calls it. The
+      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()
-      are  used  for  compiling  and matching regular expressions,
+      are  used  for compiling and matching regular expressions. A
-      while   pcre_copy_substring(),   pcre_get_substring(),   and
+      sample program that demonstrates the simplest way  of  using
-      pcre_get_substring_list()   are  convenience  functions  for
+      them  is  given in the file pcredemo.c. The pcresample docu-
-      extracting  captured  substrings  from  a  matched   subject
+      mentation describes how to run it.
-      string.  The function pcre_maketables() is used (optionally)
-      to build a set of character tables in the current locale for
+      There are convenience functions for extracting captured sub-
-      passing to pcre_compile().
+      strings from a matched subject string. They are:
-      The function pcre_info() is used  to  find  out  information
+        pcre_copy_substring()
-      about  a compiled pattern, while the function pcre_version()
+        pcre_copy_named_substring()
-      returns a pointer to a string containing the version of PCRE
+        pcre_get_substring()
-      and its date of release.
+        pcre_get_named_substring()
+        pcre_get_substring_list()
+      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 (optionally) to build
+      a  set of character tables in the current locale for passing
+      to pcre_compile().
+      The function pcre_fullinfo() is used to find out information
+      about a compiled pattern; pcre_info() is an obsolete version
+      which returns only some of the available information, but is
+      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
       contain the entry points of the standard malloc() and free()
-Line 78 
 DESCRIPTION
+Line 411 
 DESCRIPTION
       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
+      can be set by the caller to a "callout" function, which PCRE
+      will then call at specified points during a matching  opera-
+      tion. Details are given in the pcrecallout documentation.
+ MULTITHREADING
- MULTI-THREADING
       The PCRE functions can be used in  multi-threading  applica-
       tions, with the proviso that the memory management functions
-      pointed to by pcre_malloc and pcre_free are  shared  by  all
+      pointed to by pcre_malloc and  pcre_free,  and  the  callout
+      function  pointed  to  by  pcre_callout,  are  shared by all
       threads.
       The compiled form of a regular  expression  is  not  altered
-Line 91 
 MULTI-THREADING
+Line 430 
 MULTI-THREADING
       used by several threads at once.
+ CHECKING BUILD-TIME OPTIONS
+      int pcre_config(int what, void *where);
+      The function pcre_config() makes  it  possible  for  a  PCRE
+      client  to  discover  which optional features have been com-
+      piled into the PCRE library. The pcrebuild documentation has
+      more details about these optional features.
+      The first argument for pcre_config() is an integer, specify-
+      ing  which information is required; the second argument is a
+      pointer to a variable into which the information is  placed.
+      The following information is available:
+        PCRE_CONFIG_UTF8
+      The output is an integer that is set to one if UTF-8 support
+      is available; otherwise it is set to zero.
+        PCRE_CONFIG_NEWLINE
+      The output is an integer that is set to  the  value  of  the
+      code  that  is  used for the newline character. It is either
+      linefeed (10) or carriage return (13), and  should  normally
+      be the standard character for your operating system.
+        PCRE_CONFIG_LINK_SIZE
+      The output is an integer that contains the number  of  bytes
+      used  for  internal linkage in compiled regular expressions.
+      The value is 2, 3, or 4. Larger values allow larger  regular
+      expressions  to be compiled, at the expense of slower match-
+      ing. 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.
  COMPILING A PATTERN
+      pcre *pcre_compile(const char *pattern, int options,
+           const char **errptr, int *erroffset,
+           const unsigned char *tableptr);
       The function pcre_compile() is called to compile  a  pattern
       into  an internal form. The pattern is a C string terminated
       by a binary zero, and is passed in the argument  pattern.  A
       pointer  to  a  single  block of memory that is obtained via
       pcre_malloc is returned. This contains the compiled code and
-      related data. The pcre type is defined for this for conveni-
+      related  data.  The  pcre  type  is defined for the returned
-      ence, but in fact pcre is just a typedef for void, since the
+      block; this is a typedef for a structure whose contents  are
-      contents  of  the block are not externally defined. It is up
+      not  externally  defined. It is up to the caller to free the
-      to the caller to free  the  memory  when  it  is  no  longer
+      memory when it is no longer required.
-      required.
+      Although the compiled code of a PCRE regex  is  relocatable,
-      The size of a compiled pattern is  roughly  proportional  to
+      that is, it does not depend on memory location, the complete
-      the length of the pattern string, except that each character
+      pcre data block is not fully relocatable,  because  it  con-
-      class (other than those containing just a single  character,
+      tains  a  copy of the tableptr argument, which is an address
-      negated  or  not)  requires 33 bytes, and repeat quantifiers
+      (see below).
-      with a minimum greater than one or a bounded  maximum  cause
-      the  relevant  portions of the compiled pattern to be repli-
-      cated.
       The options argument contains independent bits  that  affect
       the  compilation.  It  should  be  zero  if  no  options are
       required. Some of the options, in particular, those that are
       compatible  with Perl, can also be set and unset from within
       the pattern (see the detailed description of regular expres-
-      sions below). For these options, the contents of the options
+      sions  in the pcrepattern documentation). For these options,
-      argument specifies their initial settings at  the  start  of
+      the contents of the options argument specifies their initial
-      compilation  and  execution. The PCRE_ANCHORED option can be
+      settings  at  the  start  of  compilation and execution. The
-      set at the time of matching as well as at compile time.
+      PCRE_ANCHORED option can be set at the time of  matching  as
+      well as at compile time.
       If errptr is NULL, pcre_compile() returns NULL  immediately.
       Otherwise, if compilation of a pattern fails, pcre_compile()
-Line 137 
 COMPILING A PATTERN
+Line 527 
 COMPILING A PATTERN
       must  be  the result of a call to pcre_maketables(). See the
       section on locale support below.
-      The following option bits are defined in the header file:
+      This code fragment shows a typical straightforward  call  to
+      pcre_compile():
+        pcre *re;
+        const char *error;
+        int erroffset;
+        re = pcre_compile(
+          "^A.*Z",          /* the pattern */
+,                /* default options */
+          &error,           /* for error message */
+          &erroffset,       /* for error offset */
+          NULL);            /* use default character tables */
+      The following option bits are defined:
         PCRE_ANCHORED
       If this bit is set, the pattern is forced to be  "anchored",
-      that is, it is constrained to match only at the start of the
+      that is, it is constrained to match only at the first match-
-      string which is being searched (the "subject string").  This
+      ing point in the string which is being searched  (the  "sub-
-      effect can also be achieved by appropriate constructs in the
+      ject string"). This effect can also be achieved by appropri-
-      pattern itself, which is the only way to do it in Perl.
+      ate constructs in the pattern itself, which is the only  way
+      to do it in Perl.
         PCRE_CASELESS
       If this bit is set, letters in the pattern match both  upper
       and  lower  case  letters.  It  is  equivalent  to Perl's /i
-      option.
+      option, and it can be changed within a  pattern  by  a  (?i)
+      option setting.
         PCRE_DOLLAR_ENDONLY
-Line 161 
 COMPILING A PATTERN
+Line 566 
 COMPILING A PATTERN
       character  if it is a newline (but not before any other new-
       lines).  The  PCRE_DOLLAR_ENDONLY  option  is   ignored   if
       PCRE_MULTILINE is set. There is no equivalent to this option
-      in Perl.
+      in Perl, and no way to set it within a pattern.
         PCRE_DOTALL
       If this bit is  set,  a  dot  metacharater  in  the  pattern
       matches all characters, including newlines. Without it, new-
       lines are excluded. This option is equivalent to  Perl's  /s
-      option.  A negative class such as [^a] always matches a new-
+      option,  and  it  can  be changed within a pattern by a (?s)
-      line character, independent of the setting of this option.
+      option setting. A negative class such as [^a] always matches
+      a  newline  character,  independent  of  the setting of this
+      option.
         PCRE_EXTENDED
       If this bit is set, whitespace data characters in  the  pat-
       tern  are  totally  ignored  except when escaped or inside a
-      character class, and characters between an unescaped #  out-
+      character class. Whitespace does not include the VT  charac-
-      side  a  character  class  and  the  next newline character,
+      ter  (code 11). In addition, characters between an unescaped
+      # outside a character class and the next newline  character,
       inclusive, are also ignored. This is equivalent to Perl's /x
-      option,  and  makes  it  possible to include comments inside
+      option, and it can be changed within a  pattern  by  a  (?x)
-      complicated patterns. Note, however, that this applies  only
+      option setting.
-      to  data  characters. Whitespace characters may never appear
+      This option makes it possible  to  include  comments  inside
+      complicated patterns.  Note, however, that this applies only
+      to data characters. Whitespace characters may  never  appear
       within special character sequences in a pattern, for example
-      within  the sequence (?( which introduces a conditional sub-
+      within the sequence (?( which introduces a conditional  sub-
       pattern.
         PCRE_EXTRA
-      This option turns on additional functionality of  PCRE  that
+      This option was invented in  order  to  turn  on  additional
-      is  incompatible  with Perl. Any backslash in a pattern that
+      functionality of PCRE that is incompatible with Perl, but it
-      is followed by a letter that has no special  meaning  causes
+      is currently of very little use. When set, any backslash  in
-      an  error,  thus  reserving  these  combinations  for future
+      a  pattern  that is followed by a letter that has no special
-      expansion. By default, as in Perl, a backslash followed by a
+      meaning causes an error, thus reserving  these  combinations
-      letter  with  no  special  meaning  is treated as a literal.
+      for  future  expansion.  By default, as in Perl, a backslash
-      There are at present no other features  controlled  by  this
+      followed by a letter with no special meaning is treated as a
-      option.
+      literal.  There  are at present no other features controlled
+      by this option. It can also be set by a (?X) option  setting
+      within a pattern.
         PCRE_MULTILINE
-Line 207 
 COMPILING A PATTERN
+Line 620 
 COMPILING A PATTERN
       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
+      of  line"  constructs match immediately following or immedi-
-      immediately  before  any  newline  in  the  subject  string,
+      ately before any newline  in  the  subject  string,  respec-
-      respectively,  as well as at the very start and end. This is
+      tively,  as  well  as  at  the  very  start and end. This is
-      equivalent to Perl's /m option. If there are no "\n" charac-
+      equivalent to Perl's /m option, and it can be changed within
-      ters  in  a subject string, or no occurrences of ^ or $ in a
+      a  pattern  by  a  (?m) option setting. If there are no "\n"
-      pattern, setting PCRE_MULTILINE has no effect.
+      characters in a subject string, or no occurrences of ^ or  $
+      in a pattern, setting PCRE_MULTILINE has no effect.
+        PCRE_NO_AUTO_CAPTURE
+      If this option is set, it disables the use of numbered  cap-
+      turing  parentheses  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
-Line 221 
 COMPILING A PATTERN
+Line 644 
 COMPILING A PATTERN
       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  if
+      PCRE  has  been  built to include UTF-8 support. If not, the
+      use of this option provokes an error. Details  of  how  this
+      option  changes  the behaviour of PCRE are given in the sec-
+      tion on UTF-8 support in the main pcre page.
  STUDYING A PATTERN
+      pcre_extra *pcre_study(const pcre *code, int options,
+           const char **errptr);
       When a pattern is going to be  used  several  times,  it  is
       worth  spending  more time analyzing it in order to speed up
       the time taken for matching. The function pcre_study() takes
-      a  pointer  to a compiled pattern as its first argument, and
+      a  pointer  to  a compiled pattern as its first argument. If
-      returns a  pointer  to  a  pcre_extra  block  (another  void
+      studing the pattern  produces  additional  information  that
-      typedef)  containing  additional  information about the pat-
+      will  help speed up matching, pcre_study() returns a pointer
-      tern; this can be passed to pcre_exec().  If  no  additional
+      to a pcre_extra block, in which the study_data field  points
-      information is available, NULL is returned.
+      to the results of the study.
+      The  returned  value  from  a  pcre_study()  can  be  passed
+      directly  to pcre_exec(). However, the pcre_extra block also
+      contains other fields that can be set by the  caller  before
+      the  block is passed; these are described below. If studying
+      the pattern does not  produce  any  additional  information,
+      pcre_study() returns NULL. In that circumstance, if the cal-
+      ling program wants to pass  some  of  the  other  fields  to
+      pcre_exec(), it must set up its own pcre_extra block.
       The second argument contains option  bits.  At  present,  no
       options  are  defined  for  pcre_study(),  and this argument
       should always be zero.
-      The third argument for pcre_study() is a pointer to an error
+      The third argument for pcre_study()  is  a  pointer  for  an
-      message. If studying succeeds (even if no data is returned),
+      error  message.  If  studying  succeeds  (even if no data is
-      the variable it points to  is  set  to  NULL.  Otherwise  it
+      returned), the variable it points to is set to NULL.  Other-
-      points to a textual error message.
+      wise it points to a textual error message. You should there-
+      fore  test  the  error  pointer  for  NULL   after   calling
+      pcre_study(), to be sure that it has run successfully.
+      This is a typical call to pcre_study():
+        pcre_extra *pe;
+        pe = pcre_study(
+          re,             /* result of pcre_compile() */
+,              /* no options exist */
+          &error);        /* set to NULL or points to a message */
       At present, studying a  pattern  is  useful  only  for  non-
       anchored  patterns  that do not have a single fixed starting
-Line 248 
 STUDYING A PATTERN
+Line 703 
 STUDYING A PATTERN
       created.
  LOCALE SUPPORT
       PCRE handles caseless matching, and determines whether char-
       acters  are  letters, digits, or whatever, by reference to a
-      set of tables. The library contains a default set of  tables
+      set of tables. When running in UTF-8 mode, this applies only
-      which  is  created in the default C locale when PCRE is com-
+      to characters with codes less than 256. The library contains
-      piled.  This  is   used   when   the   final   argument   of
+      a default set of tables that is created  in  the  default  C
-      pcre_compile()  is NULL, and is sufficient for many applica-
+      locale  when  PCRE  is compiled. This is used when the final
-      tions.
+      argument of pcre_compile() is NULL, and  is  sufficient  for
+      many applications.
       An alternative set of tables can, however, be supplied. Such
       tables  are built by calling the pcre_maketables() function,
-Line 274 
 LOCALE SUPPORT
+Line 730 
 LOCALE SUPPORT
       The  tables  are  built  in  memory  that  is  obtained  via
       pcre_malloc.  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 pcre_exec(). Thus
+      used via this pointer by pcre_study() and pcre_exec(). Thus,
       for any single pattern, compilation, studying  and  matching
       all happen in the same locale, but different patterns can be
       compiled in different locales. It is the caller's  responsi-
-Line 282 
 LOCALE SUPPORT
+Line 738 
 LOCALE SUPPORT
       remains available for as long as it is needed.
  INFORMATION ABOUT A PATTERN
-      The pcre_info() function returns information  about  a  com-
-      piled pattern.  Its yield is the number of capturing subpat-
+      int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
-      terns, or one of the following negative numbers:
+           int what, void *where);
+      The pcre_fullinfo() function  returns  information  about  a
+      compiled pattern. It replaces the obsolete pcre_info() func-
+      tion, which is nevertheless retained for backwards compabil-
+      ity (and is documented below).
+      The first argument for pcre_fullinfo() is a pointer  to  the
+      compiled  pattern.  The  second  argument  is  the result of
+      pcre_study(), or NULL if the pattern was  not  studied.  The
+      third  argument  specifies  which  piece  of  information is
+      required, and the fourth argument is a pointer to a variable
+      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_BADMAGIC   the "magic number" was not found
+        PCRE_ERROR_BADOPTION  the value of what was invalid
-      If the optptr argument is not NULL, a copy  of  the  options
+      Here is a typical call of  pcre_fullinfo(),  to  obtain  the
-      with which the pattern was compiled is placed in the integer
+      length of the compiled pattern:
-      it points to. These option bits are those specified  in  the
-      call  to  pcre_compile(),  modified  by any top-level option
-      settings  within  the   pattern   itself,   and   with   the
-      PCRE_ANCHORED  bit  set  if  the form of the pattern implies
-      that it can match only at the start of a subject string.
-      If the pattern is not anchored and the firstcharptr argument
+        int rc;
-      is  not  NULL, it is used to pass back information about the
+        unsigned long int length;
-      first character of any matched string. If there is  a  fixed
+        rc = pcre_fullinfo(
-      first    character,    e.g.   from   a   pattern   such   as
+          re,               /* result of pcre_compile() */
-      (cat|cow|coyote), then it is returned in the integer pointed
+          pe,               /* result of pcre_study(), or NULL */
-      to by firstcharptr. Otherwise, if either
+          PCRE_INFO_SIZE,   /* what is required */
+          &length);         /* where to put the data */
+      The possible values for the third argument  are  defined  in
+      pcre.h, and are as follows:
+        PCRE_INFO_BACKREFMAX
+      Return the number of the highest back reference in the  pat-
+      tern.  The  fourth argument should point to an int variable.
+      Zero is returned if there are no back references.
+        PCRE_INFO_CAPTURECOUNT
+      Return the number of capturing subpatterns in  the  pattern.
+      The fourth argument should point to an int variable.
+        PCRE_INFO_FIRSTBYTE
+      Return information about  the  first  byte  of  any  matched
+      string,  for a non-anchored pattern. (This option used to be
+      called PCRE_INFO_FIRSTCHAR; the old name is still recognized
+      for backwards compatibility.)
+      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
+      by where. Otherwise, if either
       (a) the pattern was compiled with the PCRE_MULTILINE option,
       and every branch starts with "^", or
-Line 312 
 INFORMATION ABOUT A PATTERN
+Line 803 
 INFORMATION ABOUT A PATTERN
       (b) every  branch  of  the  pattern  starts  with  ".*"  and
       PCRE_DOTALL is not set (if it were set, the pattern would be
       anchored),
-      then -1 is returned, indicating  that  the  pattern  matches
-      only  at  the  start  of  a subject string or after any "\n"
-      within the string. Otherwise -2 is returned.
+      -1 is returned, indicating that the pattern matches only  at
+      the  start  of  a subject string or after any newline within
+      the string. Otherwise -2 is returned. For anchored patterns,
+      -2 is returned.
+        PCRE_INFO_FIRSTTABLE
+      If the pattern was studied, and this resulted  in  the  con-
+      struction of a 256-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 returned. The fourth
+      argument should point to an unsigned char * variable.
+        PCRE_INFO_LASTLITERAL
+      Return the value of the rightmost  literal  byte  that  must
+      exist  in  any  matched  string, other than at its start, if
+      such a byte has been recorded. The  fourth  argument  should
+      point  to  an  int variable. If there 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 example, for the pattern /^a\d+z\d+/ the returned  value
+      is "z", but for /^a\dz\d/ the returned value is -1.
+        PCRE_INFO_NAMECOUNT
+        PCRE_INFO_NAMEENTRYSIZE
+        PCRE_INFO_NAMETABLE
+      PCRE supports the use of named as well as numbered capturing
+      parentheses. The names are just an additional way of identi-
+      fying the parentheses,  which  still  acquire  a  number.  A
+      caller  that  wants  to extract data from a named subpattern
+      must convert the name to a number in  order  to  access  the
+      correct  pointers  in  the  output  vector  (described  with
+      pcre_exec() below). In order to do this, it must  first  use
+      these  three  values  to  obtain  the name-to-number mapping
+      table for the pattern.
+      The  map  consists  of  a  number  of  fixed-size   entries.
+      PCRE_INFO_NAMECOUNT   gives   the  number  of  entries,  and
+      PCRE_INFO_NAMEENTRYSIZE gives the size 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  a
+      pointer to the first entry of the table (a pointer to char).
+      The first two bytes of each entry are the number of the cap-
+      turing parenthesis, most significant byte first. The rest of
+      the entry is the corresponding name,  zero  terminated.  The
+      names  are  in alphabetical order. For example, consider the
+      following pattern (assume PCRE_EXTENDED  is  set,  so  white
+      space - including newlines - is ignored):
+        (?P<date> (?P<year>(\d\d)?\d\d) -
+        (?P<month>\d\d) - (?P<day>\d\d) )
+      There are four named subpatterns,  so  the  table  has  four
+      entries,  and  each  entry in the table is eight bytes long.
+      The table is as follows, with non-printing  bytes  shows  in
+      hex, and undefined bytes shown as ??:
+01 d  a  t  e  00 ??
+05 d  a  y  00 ?? ??
+04 m  o  n  t  h  00
+02 y  e  a  r  00 ??
+      When writing code to extract data  from  named  subpatterns,
+      remember  that the length of each entry may be different for
+      each compiled pattern.
+        PCRE_INFO_OPTIONS
+      Return a copy of the options with which the pattern was com-
+      piled.  The fourth argument should point to an unsigned long
+      int variable. These option bits are those specified  in  the
+      call  to  pcre_compile(),  modified  by any top-level option
+      settings within the pattern itself.
+      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
+      Returns 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);
+      The pcre_info() function is now obsolete because its  inter-
+      face  is  too  restrictive  to return all the available data
+      about  a  compiled  pattern.   New   programs   should   use
+      pcre_fullinfo()  instead.  The  yield  of pcre_info() is the
+      number of capturing subpatterns, or  one  of  the  following
+      negative numbers:
+        PCRE_ERROR_NULL       the argument code was NULL
+        PCRE_ERROR_BADMAGIC   the "magic number" was not found
+      If the optptr argument is not NULL, a copy  of  the  options
+      with which the pattern was compiled is placed in the integer
+      it points to (see PCRE_INFO_OPTIONS above).
+      If the pattern is not anchored and the firstcharptr argument
+      is  not  NULL, it is used to pass back information about the
+      first    character    of    any    matched    string    (see
+      PCRE_INFO_FIRSTBYTE above).
  MATCHING A PATTERN
+      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 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. Otherwise this
+      study should be passed in the extra argument.
-      must be NULL.
+      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. However, if a pattern
+      ment,   whose   unused   bits  must  be  zero.  This  limits
-      was  compiled  with  PCRE_ANCHORED,  or  turned  out  to  be
+      pcre_exec() to matching at the first matching position. How-
-      anchored  by  virtue  of  its  contents,  it  cannot be made
+      ever,  if  a  pattern  was  compiled  with PCRE_ANCHORED, or
-      unachored at matching time.
+      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:
-Line 373 
 MATCHING A PATTERN
+Line 1056 
 MATCHING A PATTERN
       advancing the starting offset  (see  below)  and  trying  an
       ordinary match again.
-      The subject string is passed as  a  pointer  in  subject,  a
+      The subject string is passed to pcre_exec() as a pointer  in
-      length  in  length,  and  a  starting offset in startoffset.
+      subject,  a length in length, and a starting offset in star-
-      Unlike the pattern string, it may contain binary zero  char-
+      toffset. Unlike the pattern string, the subject may  contain
-      acters.  When  the starting offset is zero, the search for a
+      binary  zero  bytes.  When  the starting offset is zero, the
-      match starts at the beginning of the subject, and this is by
+      search for a match starts at the beginning of  the  subject,
-      far the most common case.
+      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()
-Line 471 
 MATCHING A PATTERN
+Line 1159 
 MATCHING A PATTERN
       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
+      substrings,  in  addition  to  the  offsets of the substring
-      matched by the whole pattern is (n+1)*3.
+      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:
-Line 512 
 MATCHING A PATTERN
+Line 1200 
 MATCHING A PATTERN
       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
+ EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
+      int pcre_copy_substring(const char *subject, int *ovector,
+           int stringcount, int stringnumber, char *buffer,
+           int buffersize);
+      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);
       Captured substrings can be accessed directly  by  using  the
       offsets returned by pcre_exec() in ovector. For convenience,
       the functions  pcre_copy_substring(),  pcre_get_substring(),
       and  pcre_get_substring_list()  are  provided for extracting
       captured  substrings  as  new,   separate,   zero-terminated
+      strings.  These functions identify substrings by number. The
+      next section describes functions for extracting  named  sub-
       strings.   A  substring  that  contains  a  binary  zero  is
       correctly extracted and has a further zero added on the end,
-      but the result does not, of course, function as a C string.
+      but the result is not, of course, a C string.
-      The first three arguments are the same for all  three  func-
+      The first three arguments are the  same  for  all  three  of
-      tions:  subject  is  the  subject string which has just been
+      these  functions:   subject  is the subject string which has
-      successfully matched, ovector is a pointer to the vector  of
+      just been successfully matched, ovector is a pointer to  the
-      integer   offsets   that  was  passed  to  pcre_exec(),  and
+      vector  of  integer  offsets that was passed to pcre_exec(),
-      stringcount is the number of substrings that  were  captured
+      and stringcount is the number of substrings that  were  cap-
-      by  the  match,  including  the  substring  that matched the
+      tured by the match, including the substring that matched the
       entire regular expression. This is  the  value  returned  by
       pcre_exec  if  it  is  greater  than  zero.  If  pcre_exec()
       returned zero, indicating that it ran out of space in  ovec-
-      tor, then the value passed as stringcount should be the size
+      tor,  the  value passed as stringcount should be the size of
-      of the vector divided by three.
+      the vector divided by three.
       The functions pcre_copy_substring() and pcre_get_substring()
       extract a single substring, whose number is given as string-
-Line 542 
 EXTRACTING CAPTURED SUBSTRINGS
+Line 1262 
 EXTRACTING CAPTURED SUBSTRINGS
       the entire pattern, while higher values extract the captured
       substrings. For pcre_copy_substring(), the string is  placed
       in  buffer,  whose  length is given by buffersize, while for
-      pcre_get_substring() a new block of store  is  obtained  via
+      pcre_get_substring() a new block of memory is  obtained  via
       pcre_malloc,  and its address is returned via stringptr. The
       yield of the function is  the  length  of  the  string,  not
       including the terminating zero, or one of
-Line 576 
 EXTRACTING CAPTURED SUBSTRINGS
+Line 1296 
 EXTRACTING CAPTURED SUBSTRINGS
       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
+      returned by  a  previous  call  of  pcre_get_substring()  or
+      pcre_get_substring_list(),  respectively.  They  do  nothing
+      more than call the function pointed to by  pcre_free,  which
+      of  course  could  be called directly from a C program. How-
+      ever, PCRE is used in some situations where it is linked via
+      a  special  interface  to another programming language which
+      cannot use pcre_free directly; it is for  these  cases  that
+      the functions are provided.
+ EXTRACTING CAPTURED SUBSTRINGS BY NAME
+      int pcre_copy_named_substring(const pcre *code,
+           const char *subject, int *ovector,
+           int stringcount, const char *stringname,
+           char *buffer, int buffersize);
+      int pcre_get_stringnumber(const pcre *code,
+           const char *name);
+      int pcre_get_named_substring(const pcre *code,
+           const char *subject, int *ovector,
+           int stringcount, const char *stringname,
+           const char **stringptr);
+      To extract a substring by name, you first have to find asso-
+      ciated    number.    This    can    be   done   by   calling
+      pcre_get_stringnumber(). The first argument is the  compiled
+      pattern,  and  the second is the name. For example, for this
+      pattern
+        ab(?<xxx>\d+)...
- LIMITATIONS
+      the number of the subpattern called "xxx" is  1.  Given  the
-      There are some size limitations in PCRE but it is hoped that
+      number,  you can then extract the substring directly, or use
-      they will never in practice be relevant.  The maximum length
+      one of the functions described in the previous section.  For
-      of a compiled pattern is 65539 (sic) bytes.  All  values  in
+      convenience,  there are also two functions that do the whole
-      repeating  quantifiers must be less than 65536.  The maximum
+      job.
-      number of capturing subpatterns is 99.  The  maximum  number
-      of  all  parenthesized subpatterns, including capturing sub-
+      Most of the  arguments  of  pcre_copy_named_substring()  and
-      patterns, assertions, and other types of subpattern, is 200.
+      pcre_get_named_substring()  are  the  same  as those for the
+      functions that  extract  by  number,  and  so  are  not  re-
+      described here. There are just two differences.
+      First, instead of a substring number, a  substring  name  is
+      given.  Second,  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 name-to-number trans-
+      lation table.
+      These functions  call  pcre_get_stringnumber(),  and  if  it
+      succeeds,    they   then   call   pcre_copy_substring()   or
+      pcre_get_substring(), as appropriate.
+ Last updated: 03 February 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
-      The maximum length of a subject string is the largest  posi-
+ NAME
-      tive number that an integer variable can hold. However, PCRE
+      PCRE - Perl-compatible regular expressions
-      uses recursion to handle subpatterns and indefinite  repeti-
-      tion.  This  means  that the available stack space may limit
-      the size of a subject string that can be processed  by  cer-
+ PCRE CALLOUTS
-      tain patterns.
+      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.
+ RETURN VALUES
+      The callout function returns an integer.  If  the  value  is
+      zero,  matching  proceeds as normal. If the value is greater
+      than zero, matching fails at the current  point,  but  back-
+      tracking  to test other possibilities goes ahead, just as if
+      a lookahead assertion had failed. If the value is less  than
+      zero,  the  match  is abandoned, and pcre_exec() returns the
+      value.
+      Negative values should normally be chosen from  the  set  of
+      PCRE_ERROR_xxx  values.  In  particular,  PCRE_ERROR_NOMATCH
+      forces a standard "no  match"  failure.   The  error  number
+      PCRE_ERROR_CALLOUT is reserved for use by callout functions;
+      it will never be used by PCRE itself.
+ Last updated: 21 January 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
+ NAME
+      PCRE - Perl-compatible regular expressions
  DIFFERENCES FROM PERL
-      The differences described here  are  with  respect  to  Perl
-.005.
-. By default, a whitespace character is any character  that
+      This document describes the differences  in  the  ways  that
-      the  C  library  function isspace() recognizes, though it is
+      PCRE  and  Perl  handle regular expressions. The differences
-      possible to compile PCRE  with  alternative  character  type
+      described here are with respect to Perl 5.8.
-      tables. Normally isspace() matches space, formfeed, newline,
-      carriage return, horizontal tab, and vertical tab. Perl 5 no
-      longer  includes vertical tab in its set of whitespace char-
-      acters. The \v escape that was in the Perl documentation for
-      a long time was never in fact recognized. However, the char-
-      acter itself was treated as whitespace at least up to 5.002.
-      In 5.004 and 5.005 it does not match \s.
 . 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  looka-
       head  assertions  are  counted,  but  their  entries  in the
       offsets vector are never set. Perl sets its numerical  vari-
       ables  from  any  such  patterns that are matched before the
-Line 626 
 DIFFERENCES FROM PERL
+Line 1480 
 DIFFERENCES FROM PERL
       only  if  the negative lookahead assertion contains just one
       branch.
 . Though binary zero characters are supported in  the  sub-
       ject  string,  they  are  not  allowed  in  a pattern string
       because it is passed as a normal  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,  \E, \Q. In fact these are implemented by
+      \l,  \u,  \L,  \U,  \P, \p, and \X. In fact these are imple-
-      Perl's general string-handling and are not part of its  pat-
+      mented by Perl's general string-handling and are not part of
-      tern matching engine.
+      its pattern matching engine. If any of these are encountered
+      by PCRE, an error is generated.
-. The Perl \G assertion is  not  supported  as  it  is  not
-      relevant to single pattern matches.
+. PCRE does support the \Q...\E  escape  for  quoting  sub-
+      strings. Characters in between are treated as literals. This
-. Fairly obviously, PCRE does  not  support  the  (?{code})
+      is slightly different from Perl in that $  and  @  are  also
-      construction.
+      handled  as  literals inside the quotes. In Perl, they cause
+      variable interpolation (but of course  PCRE  does  not  have
-. There are at the time of writing some  oddities  in  Perl
+      variables). Note the following examples:
-.005_02  concerned  with  the  settings of captured strings
-      when part of a pattern is repeated.  For  example,  matching
+          Pattern            PCRE matches      Perl matches
-      "aba"  against the pattern /^(a(b)?)+$/ sets $2 to the value
-      "b", but matching "aabbaa" against /^(aa(bb)?)+$/ leaves  $2
+          \Qabc$xyz\E        abc$xyz           abc followed by the
-      unset.    However,    if   the   pattern   is   changed   to
+                                                 contents of $xyz
-      /^(aa(b(b))?)+$/ then $2 (and $3) get set.
+          \Qabc\$xyz\E       abc\$xyz          abc\$xyz
+          \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
-      In Perl 5.004 $2 is set in both cases, and that is also true
-      of PCRE. If in the future Perl changes to a consistent state
+      In PCRE, the \Q...\E mechanism is not  recognized  inside  a
-      that is different, PCRE may change to follow.
+      character class.
-. Another as yet unresolved discrepancy  is  that  in  Perl
+. Fairly obviously, PCRE does not support the (?{code}) and
-.005_02  the  pattern /^(a)?(?(1)a|b)+$/ matches the string
+      (?p{code})  constructions. However, there is some experimen-
-      "a", whereas in PCRE it does not.  However, in both Perl and
+      tal support for recursive patterns using the non-Perl  items
-      PCRE /^(a)?a/ matched against "a" leaves $1 unset.
+      (?R),  (?number)  and  (?P>name).  Also,  the PCRE "callout"
+      feature allows an external function to be called during pat-
+      tern matching.
+. There are some differences that are  concerned  with  the
+      settings  of  captured  strings  when  part  of a pattern is
+      repeated. For example, matching "aba"  against  the  pattern
+      /^(a(b)?)+$/  in Perl leaves $2 unset, but in PCRE it is set
+      to "b".
 . PCRE  provides  some  extensions  to  the  Perl  regular
       expression facilities:
       (a) Although lookbehind assertions must match  fixed  length
       strings,  each  alternative branch of a lookbehind assertion
-      can match a different length of string. Perl 5.005  requires
+      can match a different length of string. Perl  requires  them
-      them all to have the same length.
+      all to have the same length.
       (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is  not
-      set,  the  $ meta- character matches only at the very end of
+      set,  the  $  meta-character matches only at the very end of
       the string.
       (c) If PCRE_EXTRA is set, a backslash followed by  a  letter
       with no special meaning is faulted.
-      (d)  If  PCRE_UNGREEDY  is  set,  the  greediness   of   the
+      (d) If PCRE_UNGREEDY is set, the greediness of  the  repeti-
-      repetition quantifiers is inverted, that is, by default they
+      tion  quantifiers  is inverted, that is, by default they are
-      are not greedy, but if followed by a question mark they are.
+      not greedy, but if followed by a question mark they are.
       (e) PCRE_ANCHORED can be used to force a pattern to be tried
-      only at the start of the subject.
+      only at the first matching position in the subject string.
+      (f)  The  PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   and
+      PCRE_NO_AUTO_CAPTURE  options  for  pcre_exec() have no Perl
+      equivalents.
+      (g) The (?R), (?number), and (?P>name) constructs allows for
+      recursive  pattern  matching  (Perl  can  do  this using the
+      (?p{code}) construct, which PCRE cannot support.)
-      (f) The PCRE_NOTBOL, PCRE_NOTEOL, and PCRE_NOTEMPTY  options
+      (h) PCRE supports  named  capturing  substrings,  using  the
-      for pcre_exec() have no Perl equivalents.
+      Python syntax.
+      (i) PCRE supports the  possessive  quantifier  "++"  syntax,
+      taken from Sun's Java package.
+      (j) The (R) condition, for  testing  recursion,  is  a  PCRE
+      extension.
+      (k) The callout facility is PCRE-specific.
+ Last updated: 03 February 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
+ NAME
+      PCRE - Perl-compatible regular expressions
+ PCRE REGULAR EXPRESSION DETAILS
- REGULAR EXPRESSION DETAILS
       The syntax and semantics of  the  regular  expressions  sup-
       ported  by PCRE are described below. Regular expressions are
       also described in the Perl documentation and in a number  of
       other  books,  some  of which have copious examples. Jeffrey
       Friedl's  "Mastering  Regular  Expressions",  published   by
-      O'Reilly  (ISBN 1-56592-257-3), covers them in great detail.
+      O'Reilly,  covers them in great detail. The description here
-      The description here is intended as reference documentation.
+      is intended as reference documentation.
+      The basic operation of PCRE is on strings of bytes. However,
+      there  is  also  support for UTF-8 character strings. To use
+      this support you must build PCRE to include  UTF-8  support,
+      and  then call pcre_compile() with the PCRE_UTF8 option. How
+      this affects the pattern matching is  mentioned  in  several
+      places  below.  There is also a summary of UTF-8 features in
+      the section on UTF-8 support in the main pcre page.
       A regular expression is a pattern that is matched against  a
       subject string from left to right. Most characters stand for
-Line 716 
 REGULAR EXPRESSION DETAILS
+Line 1609 
 REGULAR EXPRESSION DETAILS
       Outside square brackets, the meta-characters are as follows:
         \      general escape character with several uses
-        ^      assert start of  subject  (or  line,  in  multiline
+        ^      assert start of string (or line, in multiline mode)
-      mode)
+        $      assert end of string (or line, in multiline mode)
-        $      assert end of subject (or line, in multiline mode)
         .      match any character except newline (by default)
         [      start character class definition
         |      start of alternative branch
-Line 729 
 REGULAR EXPRESSION DETAILS
+Line 1621 
 REGULAR EXPRESSION DETAILS
                also quantifier minimizer
         *      0 or more quantifier
         +      1 or more quantifier
+               also "possessive quantifier"
         {      start min/max quantifier
       Part of a pattern that is in square  brackets  is  called  a
-Line 738 
 REGULAR EXPRESSION DETAILS
+Line 1631 
 REGULAR EXPRESSION DETAILS
         \      general escape character
         ^      negate the class, but only if the first character
         -      indicates character range
+        [      POSIX character class (only if followed by POSIX
+                 syntax)
         ]      terminates the character class
       The following sections describe  the  use  of  each  of  the
       meta-characters.
  BACKSLASH
       The backslash character has several uses. Firstly, if it  is
       followed  by  a  non-alphameric character, it takes away any
       special  meaning  that  character  may  have.  This  use  of
       backslash  as  an  escape  character applies both inside and
       outside character classes.
-      For example, if you want to match a "*" character, you write
+      For example, if you want to match a * character,  you  write
-      "\*" in the pattern. This applies whether or not the follow-
+      \*  in the pattern.  This escaping action applies whether or
-      ing character would otherwise  be  interpreted  as  a  meta-
+      not the following character would otherwise  be  interpreted
-      character,  so it is always safe to precede a non-alphameric
+      as  a meta-character, so it is always safe to precede a non-
-      with "\" to specify that it stands for itself.  In  particu-
+      alphameric with backslash to  specify  that  it  stands  for
-      lar, if you want to match a backslash, you write "\\".
+      itself. In particular, if you want to match a backslash, you
+      write \\.
       If a pattern is compiled with the PCRE_EXTENDED option, whi-
       tespace in the pattern (other than in a character class) and
-      characters between a "#" outside a character class  and  the
+      characters between a # outside a  character  class  and  the
       next  newline  character  are ignored. An escaping backslash
-      can be used to include a whitespace or "#" character as part
+      can be used to include a whitespace or # character  as  part
       of the pattern.
+      If you want to remove the special meaning from a sequence of
+      characters, you can do so by putting them between \Q and \E.
+      This is different from Perl in that $ and @ are  handled  as
+      literals  in  \Q...\E  sequences in PCRE, whereas in Perl, $
+      and @ cause variable interpolation. Note the following exam-
+      ples:
+        Pattern            PCRE matches   Perl matches
+        \Qabc$xyz\E        abc$xyz        abc followed by the
+                                            contents of $xyz
+        \Qabc\$xyz\E       abc\$xyz       abc\$xyz
+        \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
+      The \Q...\E sequence is recognized both inside  and  outside
+      character classes.
       A second use of backslash provides a way  of  encoding  non-
       printing  characters  in patterns in a visible manner. There
       is no restriction on the appearance of non-printing  charac-
-Line 774 
 BACKSLASH
+Line 1688 
 BACKSLASH
       usually  easier to use one of the following escape sequences
       than the binary character it represents:
-        \a     alarm, that is, the BEL character (hex 07)
+        \a        alarm, that is, the BEL character (hex 07)
-        \cx    "control-x", where x is any character
+        \cx       "control-x", where x is any character
-        \e     escape (hex 1B)
+        \e        escape (hex 1B)
-        \f     formfeed (hex 0C)
+        \f        formfeed (hex 0C)
-        \n     newline (hex 0A)
+        \n        newline (hex 0A)
-        \r     carriage return (hex 0D)
+        \r        carriage return (hex 0D)
+        \t        tab (hex 09)
-             tab (hex 09)
+        \ddd      character with octal code ddd, or backreference
-        \xhh   character with hex code hh
+        \xhh      character with hex code hh
-        \ddd   character with octal code ddd, or backreference
+        \x{hhh..} character with hex code hhh... (UTF-8 mode only)
-      The precise effect of "\cx" is as follows: if "x" is a lower
+      The precise effect of \cx is as follows: if  x  is  a  lower
       case  letter,  it  is converted to upper case. Then bit 6 of
-      the character (hex 40) is inverted.  Thus "\cz" becomes  hex
+      the character (hex 40) is inverted.  Thus  \cz  becomes  hex
-A, but "\c{" becomes hex 3B, while "\c;" becomes hex 7B.
+A, but \c{ becomes hex 3B, while \c; becomes hex 7B.
-      After "\x", up to two hexadecimal digits are  read  (letters
+      After \x, from zero  to  two  hexadecimal  digits  are  read
-      can be in upper or lower case).
+      (letters  can be in upper or lower case). In UTF-8 mode, any
+      number of hexadecimal digits may appear between \x{  and  },
+      but  the value of the character code must be less than 2**31
+      (that is, the maximum hexadecimal  value  is  7FFFFFFF).  If
+      characters  other than hexadecimal digits appear between \x{
+      and }, or if there is no terminating }, this form of  escape
+      is  not  recognized.  Instead, the initial \x will be inter-
+      preted as a basic  hexadecimal  escape,  with  no  following
+      digits, giving a byte whose value is zero.
+      Characters whose value is less than 256 can  be  defined  by
+      either  of  the  two  syntaxes  for \x when PCRE is in UTF-8
+      mode. There is no difference in the way  they  are  handled.
+      For example, \xdc is exactly the same as \x{dc}.
-      After "\0" up to two further octal digits are read. In  both
+      After \0 up to two further octal digits are  read.  In  both
       cases,  if  there are fewer than two digits, just those that
-      are present are used. Thus the sequence "\0\x\07"  specifies
+      are present are used. Thus the  sequence  \0\x\07  specifies
-      two binary zeros followed by a BEL character.  Make sure you
+      two binary zeros followed by a BEL character (code value 7).
-      supply two digits after the initial zero  if  the  character
+      Make sure you supply two digits after the  initial  zero  if
-      that follows is itself an octal digit.
+      the character that follows is itself an octal digit.
       The handling of a backslash followed by a digit other than 0
       is  complicated.   Outside  a character class, PCRE reads it
-Line 824 
 BACKSLASH
+Line 1751 
 BACKSLASH
                   writing a tab
         \011   is always a tab
         \0113  is a tab followed by the character "3"
-        \113   is the character with octal code 113 (since there
+        \113   might be a back reference, otherwise the
-                  can be no more than 99 back references)
+                  character with octal code 113
-        \377   is a byte consisting entirely of 1 bits
+        \377   might be a back reference, otherwise
+                  the byte consisting entirely of 1 bits
         \81    is either a back reference, or a binary zero
                   followed by the two characters "8" and "1"
       Note that octal values of 100 or greater must not be  intro-
       duced  by  a  leading zero, because no more than three octal
       digits are ever read.
-      All the sequences that define a single  byte  value  can  be
-      used both inside and outside character classes. In addition,
+      All the sequences that define a single byte value or a  sin-
-      inside a character class, the sequence "\b"  is  interpreted
+      gle  UTF-8 character (in UTF-8 mode) can be used both inside
-      as  the  backspace  character  (hex 08). Outside a character
+      and outside character classes. In addition, inside a charac-
-      class it has a different meaning (see below).
+      ter  class,  the sequence \b is interpreted as the backspace
+      character (hex 08). Outside a character class it has a  dif-
+      ferent meaning (see below).
       The third use of backslash is for specifying generic charac-
       ter types:
-Line 847 
 BACKSLASH
+Line 1777 
 BACKSLASH
         \s     any whitespace character
         \S     any character that is not a whitespace character
         \w     any "word" character
-        \W     any "non-word" character
+        W     any "non-word" character
       Each pair of escape sequences partitions the complete set of
       characters  into  two  disjoint  sets.  Any  given character
       matches one, and only one, of each pair.
+      In UTF-8 mode, characters with values greater than 255 never
+      match \d, \s, or \w, and always match \D, \S, and \W.
+      For compatibility with Perl, \s does not match the VT  char-
+      acter (code 11).  This makes it different from the the POSIX
+      "space" class. The \s characters are HT  (9),  LF  (10),  FF
+      (12), CR (13), and space (32).
       A "word" character is any letter or digit or the  underscore
       character,  that  is,  any  character which can be part of a
       Perl "word". The definition of letters and  digits  is  con-
       trolled  by PCRE's character tables, and may vary if locale-
-      specific matching is  taking  place  (see  "Locale  support"
+      specific matching is taking place (see "Locale  support"  in
-      above). For example, in the "fr" (French) locale, some char-
+      the pcreapi page). For example, in the "fr" (French) locale,
-      acter codes greater than 128 are used for accented  letters,
+      some character codes greater than 128 are used for  accented
-      and these are matched by \w.
+      letters, and these are matched by \w.
       These character type sequences can appear  both  inside  and
       outside  character classes. They each match one character of
-Line 875 
 BACKSLASH
+Line 1813 
 BACKSLASH
       for more complicated  assertions  is  described  below.  The
       backslashed assertions are
-        \b     word boundary
+        \b     matches at a word boundary
-        \B     not a word boundary
+        \B     matches when not at a word boundary
-        \A     start of subject (independent of multiline mode)
+        \A     matches at start of subject
-        \Z     end of subject or newline at  end  (independent  of
+        \Z     matches at end of subject or before newline at end
-      multiline mode)
+        \z     matches at end of subject
-        \z     end of subject (independent of multiline mode)
+        \G     matches at first matching position in subject
       These assertions may not appear in  character  classes  (but
-      note that "\b" has a different meaning, namely the backspace
+      note  that  \b has a different meaning, namely the backspace
       character, inside a character class).
       A word boundary is a position in the  subject  string  where
       the current character and the previous character do not both
       match \w or \W (i.e. one matches \w and  the  other  matches
       \W),  or the start or end of the string if the first or last
       character matches \w, respectively.
       The \A, \Z, and \z assertions differ  from  the  traditional
       circumflex  and  dollar  (described below) in that they only
       ever match at the very start and end of the subject  string,
-      whatever  options  are  set.  They  are  not affected by the
+      whatever options are set. Thus, they are independent of mul-
-      PCRE_NOTBOL or PCRE_NOTEOL options. If the startoffset argu-
+      tiline mode.
-      ment  of  pcre_exec()  is  non-zero, \A can never match. The
+      They are not affected  by  the  PCRE_NOTBOL  or  PCRE_NOTEOL
+      options.  If the startoffset argument of pcre_exec() is non-
+      zero, indicating that matching is to start at a point  other
+      than  the  beginning of the subject, \A can never match. The
       difference between \Z and \z is that  \Z  matches  before  a
       newline  that is the last character of the string as well as
       at the end of the string, whereas \z  matches  only  at  the
       end.
+      The \G assertion is true  only  when  the  current  matching
+      position is at the start point of the match, as specified by
+      the startoffset argument of pcre_exec(). It differs from  \A
+      when  the  value  of  startoffset  is  non-zero.  By calling
+      pcre_exec() multiple times with appropriate  arguments,  you
+      can mimic Perl's /g option, and it is in this kind of imple-
+      mentation where \G can be useful.
+      Note, however, that PCRE's  interpretation  of  \G,  as  the
+      start of the current match, is subtly different from Perl's,
+      which defines it as the end of the previous match. In  Perl,
+      these  can  be  different when the previously matched string
+      was empty. Because PCRE does just one match at  a  time,  it
+      cannot reproduce this behaviour.
+      If all the alternatives of a  pattern  begin  with  \G,  the
+      expression  is  anchored to the starting match position, and
+      the "anchored" flag is set in the compiled  regular  expres-
+      sion.
  CIRCUMFLEX AND DOLLAR
       Outside a character class, in the default matching mode, the
       circumflex  character  is an assertion which is true only if
       the current matching point is at the start  of  the  subject
       string.  If  the startoffset argument of pcre_exec() is non-
-      zero, circumflex can never match. Inside a character  class,
+      zero, circumflex  can  never  match  if  the  PCRE_MULTILINE
-      circumflex has an entirely different meaning (see below).
+      option is unset. Inside a character class, circumflex has an
+      entirely different meaning (see below).
       Circumflex need not be the first character of the pattern if
       a  number of alternatives are involved, but it should be the
-Line 932 
 CIRCUMFLEX AND DOLLAR
+Line 1895 
 CIRCUMFLEX AND DOLLAR
       The meaning of dollar can be changed so that it matches only
       at   the   very   end   of   the   string,  by  setting  the
-      PCRE_DOLLAR_ENDONLY option at compile or matching time. This
+      PCRE_DOLLAR_ENDONLY option at compile time.  This  does  not
-      does not affect the \Z assertion.
+      affect the \Z assertion.
       The meanings of the circumflex  and  dollar  characters  are
       changed  if  the  PCRE_MULTILINE option is set. When this is
       the case,  they  match  immediately  after  and  immediately
-      before an internal "\n" character, respectively, in addition
+      before an internal newline character, respectively, in addi-
-      to matching at the start and end of the subject string.  For
+      tion to matching at the start and end of the subject string.
-      example,  the  pattern  /^abc$/  matches  the subject string
+      For  example, the pattern /^abc$/ matches the subject string
       "def\nabc" in multiline  mode,  but  not  otherwise.  Conse-
       quently,  patterns  that  are  anchored  in single line mode
-      because all branches start with "^" are not anchored in mul-
+      because all branches start with ^ are not anchored in multi-
-      tiline mode, and a match for circumflex is possible when the
+      line  mode,  and a match for circumflex is possible when the
       startoffset  argument  of  pcre_exec()  is   non-zero.   The
       PCRE_DOLLAR_ENDONLY  option  is ignored if PCRE_MULTILINE is
       set.
       Note that the sequences \A, \Z, and \z can be used to  match
       the  start  and end of the subject in both modes, and if all
-      branches of a pattern start with \A is it  always  anchored,
+      branches of a pattern start with \A it is  always  anchored,
       whether PCRE_MULTILINE is set or not.
  FULL STOP (PERIOD, DOT)
       Outside a character class, a dot in the pattern matches  any
       one character in the subject, including a non-printing char-
-      acter, but not (by default)  newline.   If  the  PCRE_DOTALL
+      acter, but not (by default) newline.  In UTF-8 mode,  a  dot
-      option  is  set,  then dots match newlines as well. The han-
+      matches  any  UTF-8  character, which might be more than one
-      dling of dot is entirely independent of the handling of cir-
+      byte  long,  except  (by  default)  for  newline.   If   the
-      cumflex  and  dollar,  the only relationship being that they
+      PCRE_DOTALL  option is set, dots match newlines as well. The
-      both involve newline characters.  Dot has no special meaning
+      handling of dot is entirely independent of the  handling  of
+      circumflex and dollar, the only relationship being that they
+      both involve newline characters. Dot has no special  meaning
       in a character class.
+ MATCHING A SINGLE BYTE
+      Outside a character class, the escape  sequence  \C  matches
+      any  one  byte, both in and out of UTF-8 mode. Unlike a dot,
+      it always matches a newline. The feature is provided in Perl
+      in  order  to match individual bytes in UTF-8 mode.  Because
+      it breaks up UTF-8 characters into  individual  bytes,  what
+      remains  in  the string may be a malformed UTF-8 string. For
+      this reason it is best avoided.
+      PCRE does not allow \C to appear  in  lookbehind  assertions
+      (see below), because in UTF-8 mode it makes it impossible to
+      calculate the length of the lookbehind.
  SQUARE BRACKETS
       An opening square bracket introduces a character class, ter-
       minated  by  a  closing  square  bracket.  A  closing square
       bracket on its own is  not  special.  If  a  closing  square
-Line 976 
 SQUARE BRACKETS
+Line 1957 
 SQUARE BRACKETS
       the first data character in the class (after an initial cir-
       cumflex, if present) or escaped with a backslash.
-      A character class matches a single character in the subject;
+      A character class matches a single character in the subject.
-      the  character  must  be in the set of characters defined by
+      In  UTF-8 mode, the character may occupy more than one byte.
-      the class, unless the first character in the class is a cir-
+      A matched character must be in the set of characters defined
-      cumflex,  in which case the subject character must not be in
+      by the class, unless the first character in the class defin-
-      the set defined by the class. If a  circumflex  is  actually
+      ition is a circumflex, in which case the  subject  character
-      required  as  a  member  of  the class, ensure it is not the
+      must not be in the set defined by the class. If a circumflex
-      first character, or escape it with a backslash.
+      is actually required as a member of the class, ensure it  is
+      not the first character, or escape it with a backslash.
       For example, the character class [aeiou] matches  any  lower
       case vowel, while [^aeiou] matches any character that is not
-Line 993 
 SQUARE BRACKETS
+Line 1975 
 SQUARE BRACKETS
       string, and fails if the current pointer is at  the  end  of
       the string.
+      In UTF-8 mode, characters with values greater than  255  can
+      be  included  in a class as a literal string of bytes, or by
+      using the \x{ escaping mechanism.
       When caseless matching  is  set,  any  letters  in  a  class
       represent  both their upper case and lower case versions, so
       for example, a caseless [aeiou] matches "A" as well as  "a",
       and  a caseless [^aeiou] does not match "A", whereas a case-
-      ful version would.
+      ful version would. PCRE does not support the concept of case
+      for characters with values greater than 255.
       The newline character is never treated in any special way in
       character  classes,  whatever the setting of the PCRE_DOTALL
       or PCRE_MULTILINE options is. A  class  such  as  [^a]  will
-Line 1022 
 SQUARE BRACKETS
+Line 2008 
 SQUARE BRACKETS
       separate characters. The octal or hexadecimal representation
       of "]" can also be used to end a range.
-      Ranges operate in ASCII collating sequence. They can also be
+      Ranges  operate  in  the  collating  sequence  of  character
-      used  for  characters  specified  numerically,  for  example
+      values.  They  can  also  be  used  for characters specified
-      [\000-\037]. If a range that includes letters is  used  when
+      numerically, for example [\000-\037]. In UTF-8 mode,  ranges
-      caseless  matching  is set, it matches the letters in either
+      can  include  characters  whose values are greater than 255,
-      case. For example, [W-c] is equivalent  to  [][\^_`wxyzabc],
+      for example [\x{100}-\x{2ff}].
-      matched  caselessly,  and  if  character tables for the "fr"
-      locale are in use, [\xc8-\xcb] matches accented E characters
+      If a range that  includes  letters  is  used  when  caseless
-      in both cases.
+      matching  is set, it matches the letters in either case. For
+      example, [W-c] is  equivalent  to  [][\^_`wxyzabc],  matched
+      caselessly,  and if character tables for the "fr" locale are
+      in use, [\xc8-\xcb] matches accented E  characters  in  both
+      cases.
       The character types \d, \D, \s, \S,  \w,  and  \W  may  also
       appear  in  a  character  class, and add the characters that
-Line 1045 
 SQUARE BRACKETS
+Line 2035 
 SQUARE BRACKETS
       classes, but it does no harm if they are escaped.
+ POSIX CHARACTER CLASSES
+      Perl supports the  POSIX  notation  for  character  classes,
+      which  uses names enclosed by [: and :] within the enclosing
+      square brackets. PCRE also supports this notation. For exam-
+      ple,
+        [01[:alpha:]%]
+      matches "0", "1", any alphabetic character, or "%". The sup-
+      ported class names are
+        alnum    letters and digits
+        alpha    letters
+        ascii    character codes 0 - 127
+        blank    space or tab only
+        cntrl    control characters
+        digit    decimal digits (same as \d)
+        graph    printing characters, excluding space
+        lower    lower case letters
+        print    printing characters, including space
+        punct    printing characters, excluding letters and digits
+        space    white space (not quite the same as \s)
+        upper    upper case letters
+        word     "word" characters (same as \w)
+        xdigit   hexadecimal digits
+      The "space" characters are HT (9),  LF  (10),  VT  (11),  FF
+      (12),  CR  (13),  and  space  (32).  Notice  that  this list
+      includes the VT character (code 11). This makes "space" dif-
+      ferent  to  \s, which does not include VT (for Perl compati-
+      bility).
+      The name "word" is a Perl extension, and "blank"  is  a  GNU
+      extension from Perl 5.8. Another Perl extension is negation,
+      which is indicated by a ^ character  after  the  colon.  For
+      example,
+        [12[:^digit:]]
+      matches "1", "2", or any non-digit.  PCRE  (and  Perl)  also
+      recognize the POSIX syntax [.ch.] and [=ch=] where "ch" is a
+      "collating element", but these are  not  supported,  and  an
+      error is given if they are encountered.
+      In UTF-8 mode, characters with values greater  than  255  do
+      not match any of the POSIX character classes.
  VERTICAL BAR
       Vertical bar characters are  used  to  separate  alternative
       patterns. For example, the pattern
-Line 1062 
 VERTICAL BAR
+Line 2101 
 VERTICAL BAR
       subpattern.
  INTERNAL OPTION SETTING
-      The settings of PCRE_CASELESS, PCRE_MULTILINE,  PCRE_DOTALL,
-      and  PCRE_EXTENDED can be changed from within the pattern by
+      The   settings   of   the   PCRE_CASELESS,   PCRE_MULTILINE,
-      a sequence of Perl option letters enclosed between "(?"  and
+      PCRE_DOTALL,  and  PCRE_EXTENDED options can be changed from
-      ")". The option letters are
+      within the pattern by a  sequence  of  Perl  option  letters
+      enclosed between "(?" and ")". The option letters are
         i  for PCRE_CASELESS
         m  for PCRE_MULTILINE
-Line 1082 
 INTERNAL OPTION SETTING
+Line 2121 
 INTERNAL OPTION SETTING
       If  a  letter  appears both before and after the hyphen, the
       option is unset.
-      The scope of these option changes depends on  where  in  the
+      When an option change occurs at  top  level  (that  is,  not
-      pattern  the  setting  occurs. For settings that are outside
+      inside  subpattern  parentheses),  the change applies to the
-      any subpattern (defined below), the effect is the same as if
+      remainder of the pattern that follows.   If  the  change  is
-      the  options were set or unset at the start of matching. The
+      placed  right  at  the  start of a pattern, PCRE extracts it
-      following patterns all behave in exactly the same way:
+      into the global options (and it will therefore  show  up  in
+      data extracted by the pcre_fullinfo() function).
-        (?i)abc
-        a(?i)bc
+      An option change within a subpattern affects only that  part
-        ab(?i)c
+      of the current pattern that follows it, so
-        abc(?i)
-      which in turn is the same as compiling the pattern abc  with
-      PCRE_CASELESS  set.   In  other words, such "top level" set-
-      tings apply to the whole pattern  (unless  there  are  other
-      changes  inside subpatterns). If there is more than one set-
-      ting of the same option at top level, the rightmost  setting
-      is used.
-      If an option change occurs inside a subpattern,  the  effect
-      is  different.  This is a change of behaviour in Perl 5.005.
-      An option change inside a subpattern affects only that  part
-      of the subpattern that follows it, so
         (a(?i)b)c
-Line 1130 
 INTERNAL OPTION SETTING
+Line 2156 
 INTERNAL OPTION SETTING
       even when it is at top level. It is best put at the start.
  SUBPATTERNS
       Subpatterns are delimited by parentheses  (round  brackets),
       which can be nested.  Marking part of a pattern as a subpat-
       tern does two things:
-Line 1159 
 SUBPATTERNS
+Line 2185 
 SUBPATTERNS
         the ((red|white) (king|queen))
       the captured substrings are "red king", "red",  and  "king",
-      and are numbered 1, 2, and 3.
+      and are numbered 1, 2, and 3, respectively.
       The fact that plain parentheses fulfil two functions is  not
       always  helpful.  There are often times when a grouping sub-
       pattern is required without a capturing requirement.  If  an
-      opening parenthesis is followed by "?:", the subpattern does
+      opening  parenthesis  is  followed  by a question mark and a
-      not do any capturing, and is not counted when computing  the
+      colon, the subpattern does not do any capturing, and is  not
-      number of any subsequent capturing subpatterns. For example,
+      counted  when computing the number of any subsequent captur-
-      if the string "the white queen" is matched against the  pat-
+      ing subpatterns. For  example,  if  the  string  "the  white
-      tern
+      queen" is matched against the pattern
         the ((?:red|white) (king|queen))
       the captured substrings are "white queen" and  "queen",  and
-      are  numbered  1  and 2. The maximum number of captured sub-
+      are  numbered  1 and 2. The maximum number of capturing sub-
-      strings is 99, and the maximum number  of  all  subpatterns,
+      patterns is 65535, and the maximum depth of nesting  of  all
-      both capturing and non-capturing, is 200.
+      subpatterns, both capturing and non-capturing, is 200.
       As a  convenient  shorthand,  if  any  option  settings  are
       required  at  the  start  of a non-capturing subpattern, the
-Line 1192 
 SUBPATTERNS
+Line 2218 
 SUBPATTERNS
       the above patterns match "SUNDAY" as well as "Saturday".
+ NAMED SUBPATTERNS
+      Identifying capturing parentheses by number is  simple,  but
+      it  can be very hard to keep track of the numbers in compli-
+      cated regular expressions. Furthermore, if an expression  is
+      modified,  the  numbers  may change. To help with the diffi-
+      culty, PCRE supports the naming  of  subpatterns,  something
+      that  Perl does not provide. The Python syntax (?P<name>...)
+      is used. Names consist of alphanumeric characters and under-
+      scores, and must be unique within a pattern.
+      Named capturing parentheses are still allocated  numbers  as
+      well  as  names.  The  PCRE  API provides function calls for
+      extracting the name-to-number translation table from a  com-
+      piled  pattern. For further details see the pcreapi documen-
+      tation.
  REPETITION
       Repetition is specified by quantifiers, which can follow any
       of the following items:
+        a literal data character
-        a single character, possibly escaped
         the . metacharacter
+        the \C escape sequence
+        escapes such as \d that match single characters
         a character class
         a back reference (see next section)
-        a parenthesized subpattern (unless it is  an  assertion  -
+        a parenthesized subpattern (unless it is an assertion)
-      see below)
       The general repetition quantifier specifies  a  minimum  and
       maximum  number  of  permitted  matches,  by  giving the two
-Line 1232 
 REPETITION
+Line 2276 
 REPETITION
       as  a literal character. For example, {,6} is not a quantif-
       ier, but a literal string of four characters.
+      In UTF-8 mode, quantifiers apply to UTF-8 characters  rather
+      than  to  individual  bytes.  Thus,  for example, \x{100}{2}
+      matches two UTF-8 characters, each of which  is  represented
+      by a two-byte sequence.
       The quantifier {0} is permitted, causing the  expression  to
       behave  as  if the previous item and the quantifier were not
       present.
-Line 1270 
 REPETITION
+Line 2319 
 REPETITION
         /* first command */  not comment  /* second comment */
-      fails, because it matches  the  entire  string  due  to  the
+      fails, because it matches the entire  string  owing  to  the
       greediness of the .*  item.
-      However, if a quantifier is followed  by  a  question  mark,
+      However, if a quantifier is followed by a question mark,  it
-      then it ceases to be greedy, and instead matches the minimum
+      ceases  to be greedy, and instead matches the minimum number
-      number of times possible, so the pattern
+      of times possible, so the pattern
         /\*.*?\*/
-Line 1292 
 REPETITION
+Line 2341 
 REPETITION
       that is the only way the rest of the pattern matches.
       If the PCRE_UNGREEDY option is set (an option which  is  not
-      available  in  Perl)  then the quantifiers are not greedy by
+      available  in  Perl),  the  quantifiers  are  not  greedy by
       default, but individual ones can be made greedy by following
       them  with  a  question mark. In other words, it inverts the
       default behaviour.
-Line 1301 
 REPETITION
+Line 2350 
 REPETITION
       repeat  count  that is greater than 1 or with a limited max-
       imum, more store is required for the  compiled  pattern,  in
       proportion to the size of the minimum or maximum.
       If a pattern starts with .* or  .{0,}  and  the  PCRE_DOTALL
       option (equivalent to Perl's /s) is set, thus allowing the .
-      to match newlines, then the pattern is implicitly  anchored,
+      to match  newlines,  the  pattern  is  implicitly  anchored,
       because whatever follows will be tried against every charac-
       ter position in the subject string, so there is no point  in
       retrying  the overall match at any position after the first.
-      PCRE treats such a pattern as though it were preceded by \A.
+      PCRE normally treats such a pattern as though it  were  pre-
-      In  cases where it is known that the subject string contains
+      ceded by \A.
-      no newlines, it is worth setting PCRE_DOTALL when  the  pat-
-      tern begins with .* in order to obtain this optimization, or
+      In cases where it is known that the subject string  contains
-      alternatively using ^ to indicate anchoring explicitly.
+      no  newlines,  it  is  worth setting PCRE_DOTALL in order to
+      obtain this optimization, or alternatively using ^ to  indi-
+      cate anchoring explicitly.
+      However, there is one situation where the optimization  can-
+      not  be  used. When .*  is inside capturing parentheses that
+      are the subject of a backreference elsewhere in the pattern,
+      a match at the start may fail, and a later one succeed. Con-
+      sider, for example:
+        (.*)abc\1
+      If the subject is "xyz123abc123"  the  match  point  is  the
+      fourth  character.  For  this  reason, such a pattern is not
+      implicitly anchored.
       When a capturing subpattern is repeated, the value  captured
       is the substring that matched the final iteration. For exam-
-Line 1332 
 REPETITION
+Line 2394 
 REPETITION
       "b".
+ ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
+      With both maximizing and minimizing repetition,  failure  of
+      what  follows  normally  causes  the repeated item to be re-
+      evaluated to see if a different number of repeats allows the
+      rest  of  the  pattern  to  match. Sometimes it is useful to
+      prevent this, either to change the nature of the  match,  or
+      to  cause  it fail earlier than it otherwise might, when the
+      author of the pattern knows there is no  point  in  carrying
+      on.
+      Consider, for example, the pattern \d+foo  when  applied  to
+      the subject line
+bar
+      After matching all 6 digits and then failing to match "foo",
+      the normal action of the matcher is to try again with only 5
+      digits matching the \d+ item, and then with 4,  and  so  on,
+      before  ultimately  failing. "Atomic grouping" (a term taken
+      from Jeffrey Friedl's book) provides the means for  specify-
+      ing  that once a subpattern has matched, it is not to be re-
+      evaluated in this way.
+      If we use atomic grouping  for  the  previous  example,  the
+      matcher  would give up immediately on failing to match "foo"
+      the  first  time.  The  notation  is  a  kind   of   special
+      parenthesis, starting with (?> as in this example:
+        (?>\d+)bar
+      This kind of parenthesis "locks up" the  part of the pattern
+      it  contains once it has matched, and a failure further into
+      the pattern is prevented from backtracking  into  it.  Back-
+      tracking  past  it to previous items, however, works as nor-
+      mal.
+      An alternative description is that a subpattern of this type
+      matches  the  string  of  characters that an identical stan-
+      dalone pattern would match, if anchored at the current point
+      in the subject string.
+      Atomic grouping subpatterns are not  capturing  subpatterns.
+      Simple  cases such as the above example can be thought of as
+      a maximizing repeat that must swallow everything it can. So,
+      while both \d+ and \d+? are prepared to adjust the number of
+      digits they match in order to make the rest of  the  pattern
+      match, (?>\d+) can only match an entire sequence of digits.
+      Atomic groups in general can of course  contain  arbitrarily
+      complicated  subpatterns,  and  can be nested. However, when
+      the subpattern for an atomic group is just a single repeated
+      item,  as in the example above, a simpler notation, called a
+      "possessive quantifier" can be used.  This  consists  of  an
+      additional  +  character  following a quantifier. Using this
+      notation, the previous example can be rewritten as
+        \d++bar
+      Possessive quantifiers are always greedy; the setting of the
+      PCRE_UNGREEDY option is ignored. They are a convenient nota-
+      tion for the simpler forms of atomic group.  However,  there
+      is  no  difference in the meaning or processing of a posses-
+      sive quantifier and the equivalent atomic group.
+      The possessive quantifier syntax is an extension to the Perl
+      syntax. It originates in Sun's Java package.
+      When a pattern contains an unlimited repeat inside a subpat-
+      tern  that  can  itself  be  repeated an unlimited number of
+      times, the use of an atomic group is the only way  to  avoid
+      some  failing  matches  taking  a very long time indeed. The
+      pattern
+        (\D+|<\d+>)*[!?]
+      matches an unlimited number of substrings that  either  con-
+      sist  of  non-digits,  or digits enclosed in <>, followed by
+      either ! or ?. When it matches, it runs quickly. However, if
+      it is applied to
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+      it takes a long  time  before  reporting  failure.  This  is
+      because the string can be divided between the two repeats in
+      a large number of ways, and all have to be tried. (The exam-
+      ple  used  [!?]  rather  than a single character at the end,
+      because both PCRE and Perl have an optimization that  allows
+      for  fast  failure  when  a  single  character is used. They
+      remember the last single character that is  required  for  a
+      match,  and  fail early if it is not present in the string.)
+      If the pattern is changed to
+        ((?>\D+)|<\d+>)*[!?]
+      sequences of non-digits cannot be broken, and  failure  hap-
+      pens quickly.
  BACK REFERENCES
       Outside a character class, a backslash followed by  a  digit
       greater  than  0  (and  possibly  further  digits) is a back
-      reference to a capturing subpattern  earlier  (i.e.  to  its
+      reference to a capturing subpattern earlier (that is, to its
       left)  in  the  pattern,  provided there have been that many
       previous capturing left parentheses.
-Line 1351 
 BACK REFERENCES
+Line 2512 
 BACK REFERENCES
       A back reference matches whatever actually matched the  cap-
       turing subpattern in the current subject string, rather than
-      anything matching the subpattern itself. So the pattern
+      anything matching the subpattern itself (see "Subpatterns as
+      subroutines" below for a way of doing that). So the pattern
         (sens|respons)e and \1ibility
       matches "sense and sensibility" and "response and  responsi-
       bility",  but  not  "sense  and  responsibility". If caseful
-      matching is in force at the time of the back reference, then
+      matching is in force at the time of the back reference,  the
-      the case of letters is relevant. For example,
+      case of letters is relevant. For example,
         ((?i)rah)\s+\1
-Line 1366 
 BACK REFERENCES
+Line 2528 
 BACK REFERENCES
       though  the  original  capturing subpattern is matched case-
       lessly.
+      Back references to named subpatterns use the  Python  syntax
+      (?P=name). We could rewrite the above example as follows:
+        (?<p1>(?i)rah)\s+(?P=p1)
       There may be more than one back reference to the  same  sub-
       pattern.  If  a  subpattern  has not actually been used in a
-      particular match, then any  back  references  to  it  always
+      particular match, any back references to it always fail. For
-      fail. For example, the pattern
+      example, the pattern
         (a|(bc))\2
       always fails if it starts to match  "a"  rather  than  "bc".
-      Because  there  may  be up to 99 back references, all digits
+      Because  there  may  be many capturing parentheses in a pat-
-      following the backslash are taken as  part  of  a  potential
+      tern, all digits following the backslash are taken  as  part
-      back reference number. If the pattern continues with a digit
+      of a potential back reference number. If the pattern contin-
-      character, then some delimiter must be used to terminate the
+      ues with a digit character, some delimiter must be  used  to
-      back reference. If the PCRE_EXTENDED option is set, this can
+      terminate the back reference. If the PCRE_EXTENDED option is
-      be whitespace.  Otherwise an empty comment can be used.
+      set, this can be whitespace.  Otherwise an empty comment can
+      be used.
       A back reference that occurs inside the parentheses to which
       it  refers  fails when the subpattern is first used, so, for
-Line 1389 
 BACK REFERENCES
+Line 2557 
 BACK REFERENCES
         (a|b\1)+
-      matches any number of "a"s and also "aba", "ababaa" etc.  At
+      matches any number of "a"s and also "aba", "ababbaa" etc. At
       each iteration of the subpattern, the back reference matches
       the character string corresponding to  the  previous  itera-
       tion.  In  order  for this to work, the pattern must be such
-Line 1398 
 BACK REFERENCES
+Line 2566 
 BACK REFERENCES
       example above, or by a quantifier with a minimum of zero.
  ASSERTIONS
       An assertion is  a  test  on  the  characters  following  or
       preceding  the current matching point that does not actually
       consume any characters. The simple assertions coded  as  \b,
-      \B,  \A,  \Z,  \z, ^ and $ are described above. More compli-
+      \B,  \A, \G, \Z, \z, ^ and $ are described above.  More com-
-      cated assertions are coded as  subpatterns.  There  are  two
+      plicated assertions are coded as subpatterns. There are  two
       kinds:  those that look ahead of the current position in the
       subject string, and those that look behind it.
       An assertion subpattern is matched in the normal way, except
       that  it  does not cause the current matching position to be
       changed. Lookahead assertions start with  (?=  for  positive
-Line 1430 
 ASSERTIONS
+Line 2599 
 ASSERTIONS
       when  the  next  three  characters  are  "bar". A lookbehind
       assertion is needed to achieve this effect.
+      If you want to force a matching failure at some point  in  a
+      pattern,  the  most  convenient  way  to  do it is with (?!)
+      because an empty string always matches, so an assertion that
+      requires there not to be an empty string must always fail.
       Lookbehind assertions start with (?<=  for  positive  asser-
       tions and (?<! for negative assertions. For example,
-Line 1450 
 ASSERTIONS
+Line 2624 
 ASSERTIONS
       causes an error at compile time. Branches  that  match  dif-
       ferent length strings are permitted only at the top level of
       a lookbehind assertion. This is an extension  compared  with
-      Perl  5.005,  which  requires all branches to match the same
+      Perl  (at  least  for  5.8),  which requires all branches to
-      length of string. An assertion such as
+      match the same length of string. An assertion such as
         (?<=ab(c|de))
-Line 1465 
 ASSERTIONS
+Line 2639 
 ASSERTIONS
       alternative,  to  temporarily move the current position back
       by the fixed width and then  try  to  match.  If  there  are
       insufficient  characters  before  the  current position, the
-      match is deemed to fail.  Lookbehinds  in  conjunction  with
+      match is deemed to fail.
-      once-only  subpatterns can be particularly useful for match-
-      ing at the ends of strings; an example is given at  the  end
+      PCRE does not allow the \C escape (which  matches  a  single
-      of the section on once-only subpatterns.
+      byte  in  UTF-8  mode)  to  appear in lookbehind assertions,
+      because it makes it impossible to calculate  the  length  of
+      the lookbehind.
+      Atomic groups can be used  in  conjunction  with  lookbehind
+      assertions  to  specify efficient matching at the end of the
+      subject string. Consider a simple pattern such as
+        abcd$
+      when applied to a long string that does not  match.  Because
+      matching  proceeds  from  left  to right, PCRE will look for
+      each "a" in the subject and then see if what follows matches
+      the rest of the pattern. If the pattern is specified as
+        ^.*abcd$
+      the initial .* matches the entire string at first, but  when
+      this  fails  (because  there  is no following "a"), it back-
+      tracks to match all but the last character, then all but the
+      last  two  characters,  and so on. Once again the search for
+      "a" covers the entire string, from right to left, so we  are
+      no better off. However, if the pattern is written as
+        ^(?>.*)(?<=abcd)
+      or, equivalently,
+        ^.*+(?<=abcd)
+      there can be no backtracking for the .* item; it  can  match
+      only  the entire string. The subsequent lookbehind assertion
+      does a single test on the last four characters. If it fails,
+      the match fails immediately. For long strings, this approach
+      makes a significant difference to the processing time.
       Several assertions (of any sort) may  occur  in  succession.
       For example,
-Line 1478 
 ASSERTIONS
+Line 2686 
 ASSERTIONS
       matches "foo" preceded by three digits that are  not  "999".
       Notice  that each of the assertions is applied independently
       at the same point in the subject string. First  there  is  a
-      check  that  the  previous  three characters are all digits,
+      check that the previous three characters are all digits, and
       then there is a check that the same three characters are not
       "999".   This  pattern  does not match "foo" preceded by six
       characters, the first of which are digits and the last three
-Line 1513 
 ASSERTIONS
+Line 2721 
 ASSERTIONS
       for positive assertions, because it does not make sense  for
       negative assertions.
-      Assertions count towards the maximum  of  200  parenthesized
-      subpatterns.
- ONCE-ONLY SUBPATTERNS
-      With both maximizing and minimizing repetition,  failure  of
-      what  follows  normally  causes  the repeated item to be re-
-      evaluated to see if a different number of repeats allows the
-      rest  of  the  pattern  to  match. Sometimes it is useful to
-      prevent this, either to change the nature of the  match,  or
-      to  cause  it fail earlier than it otherwise might, when the
-      author of the pattern knows there is no  point  in  carrying
-      on.
-      Consider, for example, the pattern \d+foo  when  applied  to
-      the subject line
-bar
-      After matching all 6 digits and then failing to match "foo",
-      the normal action of the matcher is to try again with only 5
-      digits matching the \d+ item, and then with 4,  and  so  on,
-      before ultimately failing. Once-only subpatterns provide the
-      means for specifying that once a portion of the pattern  has
-      matched,  it  is  not to be re-evaluated in this way, so the
-      matcher would give up immediately on failing to match  "foo"
-      the  first  time.  The  notation  is another kind of special
-      parenthesis, starting with (?> as in this example:
-        (?>\d+)bar
-      This kind of parenthesis "locks up" the  part of the pattern
-      it  contains once it has matched, and a failure further into
-      the pattern is prevented from backtracking  into  it.  Back-
-      tracking  past  it to previous items, however, works as nor-
-      mal.
-      An alternative description is that a subpattern of this type
-      matches  the  string  of  characters that an identical stan-
-      dalone pattern would match, if anchored at the current point
-      in the subject string.
-      Once-only subpatterns are not capturing subpatterns.  Simple
-      cases  such as the above example can be thought of as a max-
-      imizing repeat that must  swallow  everything  it  can.  So,
-      while both \d+ and \d+? are prepared to adjust the number of
-      digits they match in order to make the rest of  the  pattern
-      match, (?>\d+) can only match an entire sequence of digits.
-      This construction can of course contain arbitrarily  compli-
-      cated subpatterns, and it can be nested.
-      Once-only subpatterns can be used in conjunction with  look-
-      behind  assertions  to specify efficient matching at the end
-      of the subject string. Consider a simple pattern such as
-        abcd$
-      when applied to a long  string  which  does  not  match  it.
-      Because matching proceeds from left to right, PCRE will look
-      for each "a" in the subject and then  see  if  what  follows
-      matches the rest of the pattern. If the pattern is specified
-      as
-        ^.*abcd$
-      then the initial .* matches the entire string at first,  but
-      when  this  fails,  it  backtracks to match all but the last
-      character, then all but the last two characters, and so  on.
-      Once again the search for "a" covers the entire string, from
-      right to left, so we are no better off. However, if the pat-
-      tern is written as
-        ^(?>.*)(?<=abcd)
-      then there can be no backtracking for the .*  item;  it  can
-      match  only  the  entire  string.  The subsequent lookbehind
-      assertion does a single test on the last four characters. If
-      it  fails,  the  match  fails immediately. For long strings,
-      this approach makes a significant difference to the process-
-      ing time.
  CONDITIONAL SUBPATTERNS
       It is possible to cause the matching process to obey a  sub-
       pattern  conditionally  or to choose between two alternative
       subpatterns, depending on the result  of  an  assertion,  or
-Line 1613 
 CONDITIONAL SUBPATTERNS
+Line 2738 
 CONDITIONAL SUBPATTERNS
       more than two alternatives in the subpattern, a compile-time
       error occurs.
-      There are two kinds of condition. If the  text  between  the
+      There are three kinds of condition. If the text between  the
-      parentheses  consists  of  a  sequence  of  digits, then the
+      parentheses  consists of a sequence of digits, the condition
-      condition is satisfied if the capturing subpattern  of  that
+      is satisfied if the capturing subpattern of that number  has
-      number  has  previously matched. Consider the following pat-
+      previously  matched.  The  number must be greater than zero.
-      tern, which contains non-significant white space to make  it
+      Consider  the  following  pattern,   which   contains   non-
-      more  readable  (assume  the  PCRE_EXTENDED  option)  and to
+      significant white space to make it more readable (assume the
-      divide it into three parts for ease of discussion:
+      PCRE_EXTENDED option) and to divide it into three parts  for
+      ease of discussion:
         ( \( )?    [^()]+    (?(1) \) )
-Line 1636 
 CONDITIONAL SUBPATTERNS
+Line 2762 
 CONDITIONAL SUBPATTERNS
       matches a sequence of non-parentheses,  optionally  enclosed
       in parentheses.
-      If the condition is not a sequence of digits, it must be  an
+      If the condition is the string (R), it  is  satisfied  if  a
-      assertion.  This  may be a positive or negative lookahead or
+      recursive  call  to the pattern or subpattern has been made.
-      lookbehind assertion. Consider this pattern, again  contain-
+      At "top level", the condition is  false.   This  is  a  PCRE
-      ing  non-significant  white space, and with the two alterna-
+      extension.  Recursive  patterns  are  described  in the next
-      tives on the second line:
+      section.
+      If the condition is not a sequence of digits or (R), it must
+      be  an assertion.  This may be a positive or negative looka-
+      head or lookbehind assertion. Consider this  pattern,  again
+      containing  non-significant  white  space,  and with the two
+      alternatives on the second line:
         (?(?=[^a-z]*[a-z])
         \d{2}-[a-z]{3}-\d{2}  |  \d{2}-\d{2}-\d{2} )
-Line 1655 
 CONDITIONAL SUBPATTERNS
+Line 2787 
 CONDITIONAL SUBPATTERNS
       letters and dd are digits.
  COMMENTS
       The sequence (?# marks the start of a comment which  contin-
       ues  up  to the next closing parenthesis. Nested parentheses
       are not permitted. The characters that  make  up  a  comment
-Line 1667 
 COMMENTS
+Line 2799 
 COMMENTS
       ues up to the next newline character in the pattern.
+ RECURSIVE PATTERNS
+      Consider the problem of matching a  string  in  parentheses,
+      allowing  for  unlimited nested parentheses. Without the use
+      of recursion, the best that can be done is to use a  pattern
+      that  matches  up  to some fixed depth of nesting. It is not
+      possible to handle an arbitrary nesting depth. Perl has pro-
+      vided  an  experimental facility that allows regular expres-
+      sions to recurse (amongst other things).  It  does  this  by
+      interpolating  Perl  code in the expression at run time, and
+      the code can refer to the expression itself. A Perl  pattern
+      to solve the parentheses problem can be created like this:
+        $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x;
+      The (?p{...}) item interpolates Perl code at run  time,  and
+      in  this  case refers recursively to the pattern in which it
+      appears. Obviously, PCRE cannot support the interpolation of
+      Perl  code.  Instead,  it  supports  some special syntax for
+      recursion of the entire pattern,  and  also  for  individual
+      subpattern recursion.
+      The special item that consists of (? followed  by  a  number
+      greater  than  zero and a closing parenthesis is a recursive
+      call of the subpattern of the given number, provided that it
+      occurs inside that subpattern. (If not, it is a "subroutine"
+      call, which is described in the next section.)  The  special
+      item  (?R) is a recursive call of the entire regular expres-
+      sion.
+      For example, this PCRE pattern solves the nested parentheses
+      problem  (assume  the  PCRE_EXTENDED  option  is set so that
+      white space is ignored):
+        \( ( (?>[^()]+) | (?R) )* \)
+      First it matches an opening parenthesis. Then it matches any
+      number  of substrings which can either be a sequence of non-
+      parentheses, or a recursive  match  of  the  pattern  itself
+      (that  is  a  correctly  parenthesized  substring).  Finally
+      there is a closing parenthesis.
+      If this were part of a larger pattern, you would not want to
+      recurse the entire pattern, so instead you could use this:
+        ( \( ( (?>[^()]+) | (?1) )* \) )
+      We have put the pattern into  parentheses,  and  caused  the
+      recursion  to refer to them instead of the whole pattern. In
+      a larger pattern, keeping track of parenthesis  numbers  can
+      be   tricky.   It  may  be  more  convenient  to  use  named
+      parentheses instead. For this, PCRE uses (?P>name), which is
+      an  extension  to the Python syntax that PCRE uses for named
+      parentheses (Perl does not provide  named  parentheses).  We
+      could rewrite the above example as follows:
+        (?<pn> \( ( (?>[^()]+) | (?P>pn) )* \) )
+      This particular example pattern  contains  nested  unlimited
+      repeats,  and  so  the  use  of atomic grouping for matching
+      strings of non-parentheses is important  when  applying  the
+      pattern to strings that do not match. For example, when this
+      pattern is applied to
+        (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa()
+      it yields "no match" quickly. However, if atomic grouping is
+      not used, the match runs for a very long time indeed because
+      there are so many different ways the +  and  *  repeats  can
+      carve  up  the  subject,  and  all  have to be tested before
+      failure can be reported.
+      At the end of a match, the values set for any capturing sub-
+      patterns are those from the outermost level of the recursion
+      at which the subpattern value is set.  If you want to obtain
+      intermediate  values,  a  callout  function can be used (see
+      below and the pcrecallout  documentation).  If  the  pattern
+      above is matched against
+        (ab(cd)ef)
+      the value for the capturing parentheses is  "ef",  which  is
+      the  last  value  taken  on  at the top level. If additional
+      parentheses are added, giving
+        \( ( ( (?>[^()]+) | (?R) )* ) \)
+           ^                        ^
+           ^                        ^
+      the string they capture is "ab(cd)ef", the contents  of  the
+      top  level  parentheses. If there are more than 15 capturing
+      parentheses in a pattern, PCRE has to obtain extra memory to
+      store  data  during  a  recursion,  which  it  does by using
+      pcre_malloc, freeing it  via  pcre_free  afterwards.  If  no
+      memory   can   be   obtained,   the  match  fails  with  the
+      PCRE_ERROR_NOMEMORY error.
+      Do not confuse the (?R) item with the condition  (R),  which
+      tests  for  recursion.  Consider this pattern, which matches
+      text in angle brackets, allowing for arbitrary nesting. Only
+      digits are allowed in nested brackets (that is, when recurs-
+      ing), whereas any characters  are  permitted  at  the  outer
+      level.
+        < (?: (?(R) \d++  | [^<>]*+) | (?R)) * >
+      In this pattern, (?(R) is the start of a conditional subpat-
+      tern,  with two different alternatives for the recursive and
+      non-recursive cases. The (?R) item is the  actual  recursive
+      call.
+ SUBPATTERNS AS SUBROUTINES
+      If the syntax for a recursive subpattern  reference  (either
+      by  number  or  by  name) is used outside the parentheses to
+      which it refers, it operates like a subroutine in a program-
+      ming  language. An earlier example pointed out that the pat-
+      tern
+        (sens|respons)e and \1ibility
+      matches "sense and sensibility" and "response and  responsi-
+      bility",  but not "sense and responsibility". If instead the
+      pattern
+        (sens|respons)e and (?1)ibility
+      is used, it does match "sense and responsibility" as well as
+      the other two strings. Such references must, however, follow
+      the subpattern to which they refer.
+ CALLOUTS
+      Perl has a  feature  whereby  using  the  sequence  (?{...})
+      causes  arbitrary  Perl  code  to be obeyed in the middle of
+      matching a  regular  expression.  This  makes  it  possible,
+      amongst  other  things, to extract different substrings that
+      match the same pair of parentheses when there is  a  repeti-
+      tion.
+      PCRE provides a similar feature, but  of  course  it  cannot
+      obey  arbitrary  Perl code. The feature is called "callout".
+      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. If you want to
+      identify different callout points, you can put a number less
+      than 256 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. It is
+      provided with the number of the  callout,  and,  optionally,
+      one  item  of  data  originally  supplied  by  the caller of
+      pcre_exec(). The callout  function  may  cause  matching  to
+      backtrack,  or to fail altogether. A complete description of
+      the interface to the callout function is given in the  pcre-
+      callout documentation.
+ Last updated: 03 February 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
- PERFORMANCE
+ NAME
-      Certain items that may appear in patterns are more efficient
+      PCRE - Perl-compatible regular expressions
-      than  others.  It is more efficient to use a character class
-      like [aeiou] than a set of alternatives such as (a|e|i|o|u).
-      In  general,  the  simplest  construction  that provides the
+ PCRE PERFORMANCE
-      required behaviour is usually the  most  efficient.  Jeffrey
-      Friedl's  book contains a lot of discussion about optimizing
+      Certain items that may appear in regular expression patterns
-      regular expressions for efficient performance.
+      are  more efficient than others. It is more efficient to use
+      a character class like [aeiou] than a  set  of  alternatives
-      When a pattern begins with .* and the PCRE_DOTALL option  is
+      such  as  (a|e|i|o|u). In general, the simplest construction
-      set,  the  pattern  is implicitly anchored by PCRE, since it
+      that provides the required behaviour  is  usually  the  most
-      can match only at the start of a subject string. However, if
+      efficient.  Jeffrey  Friedl's book contains a lot of discus-
-      PCRE_DOTALL  is not set, PCRE cannot make this optimization,
+      sion about optimizing regular expressions for efficient per-
-      because the . metacharacter does not then match  a  newline,
+      formance.
-      and if the subject string contains newlines, the pattern may
-      match from the character immediately following one  of  them
+      When a pattern begins with .*  not  in  parentheses,  or  in
-      instead of from the very start. For example, the pattern
+      parentheses that are not the subject of a backreference, and
+      the PCRE_DOTALL option is set,  the  pattern  is  implicitly
+      anchored  by PCRE, since it can match only at the start of a
+      subject string. However, if PCRE_DOTALL  is  not  set,  PCRE
+      cannot  make  this optimization, because the . metacharacter
+      does not then match a newline, and  if  the  subject  string
+      contains  newlines, the pattern may match from the character
+      immediately following one of them instead of from  the  very
+      start. For example, the pattern
-        (.*) second
+        .*second
       matches the subject "first\nand second" (where \n stands for
-      a newline character) with the first captured substring being
+      a newline character), with the match starting at the seventh
-      "and". In order to do this, PCRE  has  to  retry  the  match
+      character. In order to do this, PCRE has to retry the  match
       starting after every newline in the subject.
       If you are using such a pattern with subject strings that do
-Line 1713 
 PERFORMANCE
+Line 3021 
 PERFORMANCE
       that  the entire match is going to fail, PCRE has in princi-
       ple to try every possible variation, and this  can  take  an
       extremely long time.
       An optimization catches some of the more simple  cases  such
       as
-Line 1733 
 PERFORMANCE
+Line 3040 
 PERFORMANCE
       whereas the latter takes an appreciable  time  with  strings
       longer than about 20 characters.
+ Last updated: 03 February 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
+ NAME
+      PCRE - Perl-compatible regular expressions.
+ SYNOPSIS OF POSIX API
+      #include <pcreposix.h>
+      int regcomp(regex_t *preg, const char *pattern,
+           int cflags);
+      int regexec(regex_t *preg, const char *string,
+           size_t nmatch, regmatch_t pmatch[], int eflags);
+      size_t regerror(int errcode, const regex_t *preg,
+           char *errbuf, size_t errbuf_size);
+      void regfree(regex_t *preg);
+ DESCRIPTION
+      This set of functions provides a POSIX-style API to the PCRE
+      regular  expression  package.  See the pcreapi documentation
+      for a description of the native API,  which  contains  addi-
+      tional functionality.
+      The functions described here are just wrapper functions that
+      ultimately  call  the  PCRE native API. Their prototypes are
+      defined in the pcreposix.h header file, and on Unix  systems
+      the library itself is called pcreposix.a, so can be accessed
+      by adding -lpcreposix to the command for linking an applica-
+      tion  which  uses them. Because the POSIX functions call the
+      native ones, it is also necessary to add -lpcre.
+      I have implemented only those option bits that can  be  rea-
+      sonably  mapped  to  PCRE  native  options. In addition, the
+      options REG_EXTENDED and  REG_NOSUB  are  defined  with  the
+      value zero. They have no effect, but since programs that are
+      written to the POSIX interface often use them, this makes it
+      easier to slot in PCRE as a replacement library. Other POSIX
+      options are not even defined.
+      When PCRE is called via these functions, it is only the  API
+      that is POSIX-like in style. The syntax and semantics of the
+      regular expressions themselves are still those of Perl, sub-
+      ject  to  the  setting of various PCRE options, as described
+      below. "POSIX-like in style" means that the API approximates
+      to  the  POSIX definition; it is not fully POSIX-compatible,
+      and in multi-byte encoding domains it is probably even  less
+      compatible.
+      The header for these functions is supplied as pcreposix.h to
+      avoid  any  potential  clash  with other POSIX libraries. It
+      can, of course, be renamed or aliased as regex.h,  which  is
+      the "correct" name. It provides two structure types, regex_t
+      for compiled internal forms, and  regmatch_t  for  returning
+      captured  substrings.  It  also defines some constants whose
+      names start with "REG_"; these are used for setting  options
+      and identifying error codes.
+ COMPILING A PATTERN
+      The function regcomp() is called to compile a  pattern  into
+      an  internal form. The pattern is a C string terminated by a
+      binary zero, and is passed in the argument pattern. The preg
+      argument  is  a pointer to a regex_t structure which is used
+      as a base for storing information about the compiled expres-
+      sion.
+      The argument cflags is either zero, or contains one or  more
+      of the bits defined by the following macros:
+        REG_ICASE
+      The PCRE_CASELESS option  is  set  when  the  expression  is
+      passed for compilation to the native function.
+        REG_NEWLINE
+      The PCRE_MULTILINE option is  set  when  the  expression  is
+      passed  for  compilation  to  the native function. Note that
+      this  does  not  mimic  the  defined  POSIX  behaviour   for
+      REG_NEWLINE (see the following section).
+      In the absence of these flags, no options are passed to  the
+      native  function.  This means the the regex is compiled with
+      PCRE default semantics. In particular, the  way  it  handles
+      newline  characters  in  the subject string is the Perl way,
+      not the POSIX way. Note that setting PCRE_MULTILINE has only
+      some  of  the effects specified for REG_NEWLINE. It does not
+      affect the way newlines are matched by . (they aren't) or by
+      a negative class such as [^a] (they are).
+      The yield of regcomp() is zero on success, and non-zero oth-
+      erwise.  The preg structure is filled in on success, and one
+      member of the structure  is  public:  re_nsub  contains  the
+      number  of  capturing subpatterns in the regular expression.
+      Various error codes are defined in the header file.
+ MATCHING NEWLINE CHARACTERS
+      This area is not simple, because POSIX and  Perl  take  dif-
+      ferent  views  of things.  It is not possible to get PCRE to
+      obey POSIX semantics, but then PCRE was never intended to be
+      a POSIX engine. The following table lists the different pos-
+      sibilities for matching newline characters in PCRE:
+                                Default   Change with
+        . matches newline          no     PCRE_DOTALL
+        newline matches [^a]       yes    not changeable
+        $ matches \n at end        yes    PCRE_DOLLARENDONLY
+        $ matches \n in middle     no     PCRE_MULTILINE
+        ^ matches \n in middle     no     PCRE_MULTILINE
+      This is the equivalent table for POSIX:
+                                Default   Change with
+        . matches newline          yes      REG_NEWLINE
+        newline matches [^a]       yes      REG_NEWLINE
+        $ matches \n at end        no       REG_NEWLINE
+        $ matches \n in middle     no       REG_NEWLINE
+        ^ matches \n in middle     no       REG_NEWLINE
+      PCRE's behaviour is the same as Perl's, except that there is
+      no  equivalent  for PCRE_DOLLARENDONLY in Perl. In both PCRE
+      and Perl, there is no way  to  stop  newline  from  matching
+      [^a].
+      The default POSIX newline handling can be obtained  by  set-
+      ting PCRE_DOTALL and PCRE_DOLLARENDONLY, but there is no way
+      to make PCRE behave exactly as for the REG_NEWLINE action.
+ MATCHING A PATTERN
+      The function regexec() is called  to  match  a  pre-compiled
+      pattern  preg against a given string, which is terminated by
+      a zero byte, subject to the options in eflags. These can be:
+        REG_NOTBOL
+      The PCRE_NOTBOL option is set when  calling  the  underlying
+      PCRE matching function.
+        REG_NOTEOL
+      The PCRE_NOTEOL option is set when  calling  the  underlying
+      PCRE matching function.
+      The portion of the string that was  matched,  and  also  any
+      captured  substrings,  are returned via the pmatch argument,
+      which points to  an  array  of  nmatch  structures  of  type
+      regmatch_t,  containing  the  members rm_so and rm_eo. These
+      contain the offset to the first character of each  substring
+      and  the offset to the first character after the end of each
+      substring, respectively.  The  0th  element  of  the  vector
+      relates  to  the  entire portion of string that was matched;
+      subsequent elements relate to the capturing  subpatterns  of
+      the  regular  expression.  Unused  entries in the array have
+      both structure members set to -1.
+      A successful match yields a zero return; various error codes
+      are  defined in the header file, of which REG_NOMATCH is the
+      "expected" failure code.
+ ERROR MESSAGES
+      The regerror()  function  maps  a  non-zero  errorcode  from
+      either  regcomp()  or  regexec()  to a printable message. If
+      preg is not NULL, the error should have arisen from the  use
+      of  that structure. A message terminated by a binary zero is
+      placed in errbuf. The length of the message,  including  the
+      zero,  is  limited to errbuf_size. The yield of the function
+      is the size of buffer needed to hold the whole message.
+ STORAGE
+      Compiling a regular expression causes memory to be allocated
+      and  associated  with  the preg structure. The function reg-
+      free() frees all such memory, after which preg may no longer
+      be used as a compiled expression.
  AUTHOR
       Philip Hazel <ph10@cam.ac.uk>
       University Computing Service,
-      New Museums Site,
       Cambridge CB2 3QG, England.
-      Phone: +44 1223 334714
-      Last updated: 29 July 1999
+ Last updated: 03 February 2003
-      Copyright (c) 1997-1999 University of Cambridge.
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------
+ NAME
+      PCRE - Perl-compatible regular expressions
+ PCRE SAMPLE PROGRAM
+      A simple, complete demonstration program, to get you started
+      with  using  PCRE, is supplied in the file pcredemo.c in the
+      PCRE distribution.
+      The program compiles the  regular  expression  that  is  its
+      first argument, and matches it against the subject string in
+      its second argument. No PCRE options are  set,  and  default
+      character tables are used. If matching succeeds, the program
+      outputs the portion of the subject  that  matched,  together
+      with the contents of any captured substrings.
+      If the -g option is given on the command line,  the  program
+      then  goes on to check for further matches of the same regu-
+      lar expression in the same subject string. The  logic  is  a
+      little  bit tricky because of the possibility of matching an
+      empty string. Comments in the code explain what is going on.
+      On a Unix system that has PCRE installed in /usr/local,  you
+      can  compile  the demonstration program using a command like
+      this:
+        gcc -o pcredemo pcredemo.c -I/usr/local/include \
+            -L/usr/local/lib -lpcre
+      Then you can run simple tests like this:
+        ./pcredemo 'cat|dog' 'the cat sat on the mat'
+        ./pcredemo -g 'cat|dog' 'the dog sat on the cat'
+      Note that there is a much more comprehensive  test  program,
+      called  pcretest,  which  supports  many more facilities for
+      testing  regular  expressions  and  the  PCRE  library.  The
+      pcredemo program is provided as a simple coding example.
+      On some operating systems (e.g.  Solaris)  you  may  get  an
+      error like this when you try to run pcredemo:
+        ld.so.1: a.out: fatal: libpcre.so.0: open failed: No  such
+      file or directory
+      This is caused by the way shared library  support  works  on
+      those systems. You need to add
+        -R/usr/local/lib
+      to the compile command to get round this problem.
+ Last updated: 28 January 2003
+ Copyright (c) 1997-2003 University of Cambridge.
+ -----------------------------------------------------------------------------

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