NAME
       library - standard library of Tcl procedures

SYNOPSIS
       auto_execok cmd
       auto_load cmd
       auto_mkindex dir pattern pattern ...
       auto_mkindex_old dir pattern pattern ...
       auto_reset
       tcl_findLibrary basename version patch initScript enVarName varName
       parray arrayName
       tcl_endOfWord str start
       tcl_startOfNextWord str start
       tcl_startOfPreviousWord str start
       tcl_wordBreakAfter str start
       tcl_wordBreakBefore str start


INTRODUCTION
       Tcl  includes  a  library  of Tcl procedures for commonly-
       needed functions.   The  procedures  defined  in  the  Tcl
       library   are  generic  ones  suitable  for  use  by  many
       different applications.  The location of the  Tcl  library
       is  returned  by the info library command.  In addition to
       the Tcl library, each application will normally  have  its
       own  library  of support procedures as well;  the location
       of this library is normally given  by  the  value  of  the
       $app_library global variable, where app is the name of the
       application.  For example, the location of the Tk  library
       is kept in the variable $tk_library.

       To   access   the   procedures  in  the  Tcl  library,  an
       application  should  source  the  file  init.tcl  in   the
       library, for example with the Tcl command
              source [file join [info library] init.tcl]
       If  the  library  procedure  Tcl_Init  is  invoked from an
       application's   Tcl_AppInit   procedure,   this    happens
       automatically.   The  code  in  init.tcl  will  define the
       unknown procedure and arrange for the other procedures  to
       be  loaded on-demand using the auto-load mechanism defined
       below.


COMMAND PROCEDURES
       The following procedures are provided in the Tcl library:

       auto_execok cmd
              Determines whether there is an executable  file  or
              shell builtin by the name cmd.  If so, it returns a
              list of arguments to be passed to exec  to  execute
              the  executable file or shell builtin named by cmd.
              If not, it returns an empty string.   This  command
              examines the directories in the current search path
              (given by the PATH  environment  variable)  in  its
              search  for  an  executable  file  named  cmd.   On
              Windows platforms, the search is expanded with  the
              same  directories  and  file  extensions as used by
              exec.   Auto_exec   remembers   information   about
              previous  searches  in  an  array named auto_execs;
              this avoids the path search in future calls for the
              same  cmd.   The  command auto_reset may be used to
              force auto_execok to forget its cached information.

       auto_load cmd
              This  command attempts to load the definition for a
              Tcl command named cmd.  To do this, it searches  an
              auto-load  path,  which  is  a  list of one or more
              directories.  The auto-load path is  given  by  the
              global  variable $auto_path if it exists.  If there
              is no  $auto_path  variable,  then  the  TCLLIBPATH
              environment   variable   is  used,  if  it  exists.
              Otherwise the auto-load path consists of  just  the
              Tcl  library  directory.   Within each directory in
              the auto-load path there must be  a  file  tclIndex
              that describes one or more commands defined in that
              directory and a script to evaluate to load each  of
              the   commands.    The   tclIndex  file  should  be
              generated with the auto_mkindex command.  If cmd is
              found in an index file, then the appropriate script
              is evaluated to create the command.  The  auto_load
              command  returns 1 if cmd was successfully created.
              The command returns 0 if there was no  index  entry
              for cmd or if the script didn't actually define cmd
              (e.g. because index information is  out  of  date).
              If  an  error  occurs  while processing the script,
              then that error is returned.  Auto_load only  reads
              the  index  information  once  and  saves it in the
              array auto_index;  future calls to auto_load  check
              for  cmd  in  the  array rather than re-reading the
              index files.  The cached index information  may  be
              deleted  with  the  command  auto_reset.  This will
              force the next  auto_load  command  to  reload  the
              index database from disk.

       auto_mkindex dir pattern pattern ...
              Generates  an  index suitable for use by auto_load.
              The command searches dir for all files whose  names
              match  any  of  the  pattern arguments (matching is
              done with the glob command), generates an index  of
              all  the  Tcl command procedures defined in all the
              matching files, and stores the index information in
              a  file  named  tclIndex  in dir.  If no pattern is
              given a pattern of  *.tcl  will  be  assumed.   For
              example, the command
                     auto_mkindex foo *.tcl

              will  read  all  the .tcl files in subdirectory foo
              and generate a new index file foo/tclIndex.

              Auto_mkindex parses the  Tcl  scripts  by  sourcing
              them  into  a  slave interpreter and monitoring the
              proc and  namespace  commands  that  are  executed.
              Extensions     can     use    the    (undocumented)
              auto_mkindex_parser  package  to   register   other
              commands  that  can  contribute  to  the  auto_load
              index.  You will have to read through  auto.tcl  to
              see how this works.

              Auto_mkindex_old   parses  the  Tcl  scripts  in  a
              relatively  unsophisticated  way:   if   any   line
              contains the word proc as its first characters then
              it is assumed to be a procedure definition and  the
              next  word  of the line is taken as the procedure's
              name.  Procedure definitions that don't  appear  in
              this  way  (e.g.  they have spaces before the proc)
              will not  be  indexed.   If  your  script  contains
              "dangerous"  code,  such  as  global initialization
              code or procedure  names  with  special  characters
              like   $,   *,   [   or  ],  you  are  safer  using
              auto_mkindex_old.

       auto_reset
              Destroys all the information cached by  auto_execok
              and  auto_load.   This  information will be re-read
              from disk the next time it is  needed.   Auto_reset
              also deletes any procedures listed in the auto-load
              index, so that fresh copies of them will be  loaded
              the next time that they're used.

       tcl_findLibrary   basename  version  patch  initScript
       enVarName varName
              This  is  a  standard  search  procedure for use by
              extensions during their initialization.  They  call
              this  procedure to look for their script library in
              several standard directories.  The  last  component
              of  the  name  of the library directory is normally
              basenameversion (e.g.,  tk8.0),  but  it  might  be
              "library"  when  in  the  build  hierarchies.   The
              initScript  file   will   be   sourced   into   the
              interpreter  once  it  is  found.  The directory in
              which this file is found is stored into the  global
              variable  varName.   If  this  variable  is already
              defined  (e.g.,  by  C  code   during   application
              initialization)   then   no   searching   is  done.
              Otherwise the search looks  in  these  directories:
              the  directory  named  by  the environment variable
              enVarName; relative to the Tcl  library  directory;
              relative  to  the  executable  file in the standard
              installation bin or bin/arch directory; relative to
              the  executable  file  in  the  current build tree;
              relative to the executable file in a parallel build
              tree.

       parray arrayName
              Prints  on  standard output the names and values of
              all the elements in the array arrayName.  ArrayName
              must  be  an  array  accessible  to  the  caller of
              parray.  It may be either local or global.

       tcl_endOfWord str start
              Returns the index of the first end-of-word location
              that  occurs  after  a  starting index start in the
              string str.  An end-of-word location is defined  to
              be the first non-word character following the first
              word character after the starting  point.   Returns
              -1 if there are no more end-of-word locations after
              the  starting  point.   See  the   description   of
              tcl_wordchars  and  tcl_nonwordchars below for more
              details on how Tcl determines which characters  are
              word characters.

       tcl_startOfNextWord str start
              Returns   the  index  of  the  first  start-of-word
              location that occurs after a starting  index  start
              in  the  string  str.   A start-of-word location is
              defined to be the first word character following  a
              non-word  character.   Returns  -1  if there are no
              more start-of-word  locations  after  the  starting
              point.

       tcl_startOfPreviousWord str start
              Returns   the  index  of  the  first  start-of-word
              location that occurs before a starting index  start
              in the string str.  Returns -1 if there are no more
              start-of-word locations before the starting  point.

       tcl_wordBreakAfter str start
              Returns  the index of the first word boundary after
              the  starting  index  start  in  the  string   str.
              Returns  -1  if  there are no more boundaries after
              the starting point in the given string.  The  index
              returned refers to the second character of the pair
              that comprises a boundary.

       tcl_wordBreakBefore str start
              Returns the index of the first word boundary before
              the   starting  index  start  in  the  string  str.
              Returns -1 if there are no more  boundaries  before
              the  starting point in the given string.  The index
              returned refers to the second character of the pair
              that comprises a boundary.


VARIABLES
       The  following global variables are defined or used by the
       procedures in the Tcl library:

       auto_execs
              Used by auto_execok  to  record  information  about
              whether  particular  commands  exist  as executable
              files.

       auto_index
              Used by auto_load to  save  the  index  information
              read from disk.

       auto_noexec
              If  set to any value, then unknown will not attempt
              to auto-exec any commands.

       auto_noload
              If set to any value, then unknown will not  attempt
              to auto-load any commands.

       auto_path
              If  set,  then  it  must  contain  a valid Tcl list
              giving  directories  to  search  during   auto-load
              operations.   This  variable  is initialized during
              startup  to  contain,  in  order:  the  directories
              listed  in the TCLLIBPATH environment variable, the
              directory named by the $tcl_library  variable,  the
              parent  directory  of $tcl_library, the directories
              listed in the $tcl_pkgPath variable.

       env(TCL_LIBRARY)
              If set, then  it  specifies  the  location  of  the
              directory  containing library scripts (the value of
              this variable will be assigned to  the  tcl_library
              variable and therefore returned by the command info
              library).   If  this  variable  isn't  set  then  a
              default value is used.

       env(TCLLIBPATH)
              If  set,  then  it  must  contain  a valid Tcl list
              giving  directories  to  search  during   auto-load
              operations.   Directories  must be specified in Tcl
              format, using "/" as the path separator, regardless
              of  platform.   This  variable  is  only  used when
              initializing the auto_path variable.

       tcl_nonwordchars
              This variable contains a regular expression that is
              used  by  routines  like  tcl_endOfWord to identify
              whether a character is part of a word or  not.   If
              the  pattern  matches a character, the character is
              considered to be a non-word character.  On  Windows
              platforms,   spaces,   tabs,   and   newlines   are
              considered  non-word   characters.    Under   Unix,
              everything but numbers, letters and underscores are
              considered non-word characters.

       tcl_wordchars
              This variable contains a regular expression that is
              used  by  routines  like  tcl_endOfWord to identify
              whether a character is part of a word or  not.   If
              the  pattern  matches a character, the character is
              considered to be  a  word  character.   On  Windows
              platforms,  words  are  comprised  of any character
              that is not a space, tab, or newline.  Under  Unix,
              words   are   comprised   of  numbers,  letters  or
              underscores.

       unknown_pending
              Used by unknown to record the command(s) for  which
              it is searching.  It is used to detect errors where
              unknown  recurses  on   itself   infinitely.    The
              variable is unset before unknown returns.


SEE ALSO
       re_syntax(n)


KEYWORDS
