NAME
       unknown - Handle attempts to use non-existent commands

SYNOPSIS
       unknown cmdName ?arg arg ...?


DESCRIPTION
       This  command  doesn't  actually exist as part of Tcl, but
       Tcl will invoke it if it does exist.  If  the  Tcl  inter-
       preter  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
