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

______________________________________________________________________________

NAME
       auto_execok,   auto_import,   auto_load,	  auto_mkindex,	 auto_qualify,
       auto_reset,	 tcl_findLibrary,	 parray,	tcl_endOfWord,
       tcl_startOfNextWord,    tcl_startOfPreviousWord,	   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_qualify command namespace
       auto_reset
       tcl_findLibrary basename	version	patch initScript enVarName varName
       parray arrayName	?pattern?
       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	proce-
       dures  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 com-
       mand

	      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_execok 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_import pattern
	      Auto_import is invoked during namespace import to	see if the im-
	      ported commands specified	by pattern reside in an	autoloaded li-
	      brary.   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 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 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 suc-
	      cessfully	created.  The command returns 0	if there was no	 index
	      entry for	cmd or if the script did not 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	(which	has  the  same syntax as auto_mkindex)
	      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 defini-
	      tions that do not	appear in this way (e.g. they have spaces  be-
	      fore  the	 proc)	will  not be indexed.  If your script contains
	      "dangerous" code,	such as	global initialization code  or	proce-
	      dure  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	are 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 command in  the	current	 name-
	      space,  and  then	in the global namespace.  Accordingly, if com-
	      mand is relative and namespace is	not ::,	the list returned  has
	      two elements:  command scoped by namespace, as if	it were	a com-
	      mand 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-loading of functions at runtime.

       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 base-
	      nameversion (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  environ-
	      ment  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	paral-
	      lel build	tree.

       parray arrayName	?pattern?
	      Prints  on  standard output the names and	values of all the ele-
	      ments in the array arrayName, or just the	names that match  pat-
	      tern (using the matching rules of	string match) and their	values
	      if pattern is given.  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_nonword-
	      chars below for more details on how Tcl determines which charac-
	      ters are word characters.

       tcl_startOfNextWord str start
	      Returns the index	of the first start-of-word location  that  oc-
	      curs  after  a starting index start in the string	str.  A	start-
	      of-word location is defined to be	the first word character  fol-
	      lowing  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  oc-
	      curs  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.	They fall into two  broad  classes,  handling  unknown
       commands	and packages, and determining what are words.

   AUTOLOADING AND PACKAGE MANAGEMENT VARIABLES
       auto_execs
	      Used by auto_execok to record information	about whether particu-
	      lar 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 (including for package in-
	      dex files	when using the default package unknown handler).  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 global variable, the	parent
	      directory	of tcl_library,	the directories	listed in the tcl_pkg-
	      Path variable.  Additional locations to look for files and pack-
	      age indices should normally be added to this variable using lap-
	      pend.

       env(TCL_LIBRARY)
	      If set, then it specifies	the location of	the directory contain-
	      ing library scripts (the value of	this variable will be assigned
	      to  the  tcl_library variable and	therefore returned by the com-
	      mand info	library).  If this variable is not 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, re-
	      gardless of platform.  This variable is only used	when  initial-
	      izing the	auto_path variable.

   WORD	BOUNDARY DETERMINATION VARIABLES
       These	variables    are    only    used    in	  the	tcl_endOfWord,
       tcl_startOfNextWord, tcl_startOfPreviousWord,  tcl_wordBreakAfter,  and
       tcl_wordBreakBefore commands.

       tcl_nonwordchars
	      This variable contains a regular expression that is used by rou-
	      tines like tcl_endOfWord to identify whether a character is part
	      of a word	or not.	 If the	pattern	matches	a character, the char-
	      acter 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 un-
	      derscores	are considered non-word	characters.

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

SEE ALSO
       env(n), info(n),	re_syntax(n)

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

Tcl				      8.0			    library(n)

NAME | SYNOPSIS | INTRODUCTION | COMMAND PROCEDURES | VARIABLES | SEE ALSO | KEYWORDS

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