listen command

    (A) Function
        Switching an input place of a script (listening-stream) to another, 
        and restarting a command interpreter. 

    (B) Format

        [ listen ]  <file>  { <argument> }


    (C) Parameters

       <file>
          Designate the name of a file in which a script is.

       <argument>
          Define an argument macro to be passed to the script. 

    (D) Notes
        The argument macro "$0" in a script is "listen".
        If a command name other than those listed in this chapter is specified,
        it is interpreted as the listen command whose command name part is omitted. 
        If you want to change a listening-stream to a character string, 
        use the eval command. 
        A script that contains the listen command is first pushed to a stack.
        After a new script ends, the stacked script is retrieved and then 
        resumes the suspended execution. 

    (E) Related items
        eval command
        leave command
        define command
        setenv command
        shift command