NAME
       library - standard library of Tcl procedures

SYNOPSIS
       auto_execok cmd
       auto_load cmd
       auto_mkindex dir pattern pattern ...
       auto_reset
       parray arrayName


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 differ-
       ent 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 applica-
       tion 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 automat-
       ically.  The code in init.tcl will define the unknown pro-
       cedure 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 by
              the name cmd.  This command examines  the  directo-
              ries  in the current search path (given by the PATH
              environment variable) to see if there  is  an  exe-
              cutable file named cmd in any of those directories.
              If  so,  it  returns  1;   if  not  it  returns  0.
              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.  Other-
              wise 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 gener-
              ated 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 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.

       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.

       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  par-
              ray.  It may be either local or global.


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 giv-
              ing directories to search during  auto-load  opera-
              tions.

       env(TCL_LIBRARY)
              If  set,  then  it  specifies  the  location of the
              directory containing library scripts (the value  of
              this  variable will be 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 giv-
              ing directories to search during  auto-load  opera-
              tions.   This variable is only used if auto_path is
              not defined.

       unknown_active
              This variable is set by unknown to indicate that it
              is  active.   It  is  used  to  detect errors where
              unknown recurses on itself infinitely.   The  vari-
              able is unset before unknown returns.


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