unknown(n)                   Tcl ( )                   unknown(n)



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     NAME
          unknown - Handle attempts to use non-existent commands

     SYNOPSIS
          unknown cmdName ?arg arg ...?
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     DESCRIPTION
          This command doesn't actually exist as part of Tcl, but  Tcl
          will  invoke  it  if  it does exist.  If the Tcl interpreter
          encounters a command name for which there is not  a  defined
          command,  then  Tcl  checks  for  the existence of a command
          named unknown.  If  there  is  no  such  command,  then  the
          interpreter  returns  an  error.   If  the  unknown  command
          exists, then it is invoked with arguments consisting of  the
          fully-substituted  name  and arguments for the original non-
          existent command.  The unknown command typically does things
          like  searching  through  library  directories for a command
          procedure with the name cmdName,  or  expanding  abbreviated
          command  names  to  full-length,  or automatically executing
          unknown commands as sub-processes.  In some cases  (such  as
          expanding  abbreviations)  unknown  will change the original
          command slightly and then (re-)execute it.   The  result  of
          the  unknown  command is used as the result for the original
          non-existent command.


     KEYWORDS
          error, non-existent command























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