I would like to use the "at" command for starting a shell script (at a later time) that opens a window or puts graphic to the X root background (like xv -root). Unfortunately, it does not work because it does not have permission to send anything to the display. The message I get is: "Gdk-WARNING **: cannot open display:"

The script is started properly and works fine. Only the part that should put up graphic to the display does not work, i.e. does not get permission to do so.
Of course, X access is allowed (with xhost +).

I have the impression that the "at" command is intended only for line command scripts that do not open windows or such.
Is there any workaround?

btw, I want to use "at" as user, not as root.

I've been looking for manuals, faqs and docs for hours now, without success.

Try setting the DISPLAY variable in your shell script...

export DISPLAY=:0


Matt

Thanks for your answer!! It's working now!

Here's the complete solution (in case someone has the same problem):

"at" forces your shell script to run in /bin/sh, even if you prepend an #!/bin/bash in your script.
and for some reason, in sh the environment variables seem to be reset to its prior values immediately after being set. so you have to do an
env DISPLAY=:0 xterm
in one command.