[chchar]
> I have one very simple ruby program. (Please see below).
> When I try to run my program as below, it prompt me error.
> 
> [root@abc sample]# ruby test.rb 
> /usr/local/lib/ruby/1.6/tk.rb:468:in `new': no display name and no $DISPLAY
> environment variabl

This is a unix problem, not a ruby problem. In unices, the DISPLAY
environment variable specifies the currently active X-display. If DISPLAY
is not set, the system does not know about any graphic display and therefore
cannot display graphics (such as a Tk window).

I would guess that you get this error when running ruby over a telnet
connection. If you want to display graphics with a telnet connection you
need to run an X server on your local machine and set the DISPLAY variable
on the remote machine to point to that X server. Look at "man X" to get
started.

// Niklas