unknown(3Tcl)							 unknown(3Tcl)

NAME    [Toc]    [Back]

     unknown - Handle attempts to use non-existent commands

SYNOPSIS    [Toc]    [Back]

     unknown cmdName ?arg arg ...?

DESCRIPTION    [Toc]    [Back]

     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    [Toc]    [Back]

     error, non-existent command


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