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library(n)			      Tcl Built-In Commands			       library(n)

_________________________________________________________________________________________________

NAME
       auto_execok,   auto_import,   auto_load,   auto_mkindex,  auto_mkindex_old,  auto_qualify,
       auto_reset, tcl_findLibrary, parray, tcl_endOfWord, tcl_startOfNextWord, tcl_startOfPrevi-
       ousWord, tcl_wordBreakAfter, tcl_wordBreakBefore - standard library of Tcl procedures

SYNOPSIS
       auto_execok cmd
       auto_import pattern
       auto_load cmd
       auto_mkindex dir pattern pattern ...
       auto_mkindex_old dir pattern pattern ...
       auto_qualify command namespace
       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  applica-
       tions.  The location of the Tcl library is returned by the info library command.  In addi-
       tion 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  exe-
	      cutable  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 infor-
	      mation.

       auto_import pattern
	      Auto_import is invoked during namespace import to  see  if  the  imported  commands
	      specified  by  pattern  reside  in  an autoloaded library.  If so, the commands are
	      loaded so that they will be available to the interpreter for  creating  the  import
	      links.   If  the	commands do not reside in an autoloaded library, auto_import does
	      nothing.	The pattern matching is performed according  to  the  matching	rules  of
	      namespace import.

       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 direc-
	      tory.  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 eval-
	      uate 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.

       auto_qualify command namespace
	      Computes a list of fully qualified names for command.  This list mirrors the path a
	      standard Tcl interpreter follows for command lookups:  first it looks for the  com-
	      mand  in	the current namespace, and then in the global namespace.  Accordingly, if
	      command is relative and namespace is not ::, the list returned  has  two	elements:
	      command  scoped  by  namespace, as if it were a command in the namespace namespace;
	      and command as if it were a command in the global namespace.  Otherwise, if  either
	      command is absolute (it begins with ::), or namespace is ::, the list contains only
	      command as if it were a command in the global namespace.

	      Auto_qualify is used by the auto-loading facilities  in  Tcl,  both  for	producing
	      auto-loading indexes such as pkgIndex.tcl, and for performing the actual auto-load-
	      ing of functions at runtime.

       tcl_findLibrary basename version patch initScript enVarName varName
	      This is a standard search procedure for use by extensions during their  initializa-
	      tion.   They  call this procedure to look for their script library in several stan-
	      dard directories.  The last component of the name of the library directory is  nor-
	      mally  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 vari-
	      able varName.  If this variable is already defined (e.g., by C code during applica-
	      tion  initialization)  then  no  searching  is done.  Otherwise the search looks in
	      these directories: the directory named by the environment variable enVarName; rela-
	      tive  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 cur-
	      rent 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 loca- |
	      tions 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 there-
	      fore 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 ini-
	      tializing the auto_path variable.

       tcl_nonwordchars
	      This variable contains a regular expression that is used by routines like  tcl_end- |
	      OfWord  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_end- |
	      OfWord 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 Win- |
	      dows 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
       info(n), re_syntax(n)

KEYWORDS
       auto-exec, auto-load, library, unknown, word, whitespace

Tcl					       8.0				       library(n)
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