can't fined the ms-dos command "at" for ubunto

at is a linux command at a set time

at 3:30 tomorrow
at>clamscan -i /home/andy > mail <email address hidden>
at> <CTRL-D>
job 3 at 2005-04-28 03:30

This schedules a virus scan of my home drive at 3:30am

You should look into making your script a cron job. For more information about cron run the command

man cron

and read this link:

https://help.ubuntu.com/community/CronHowto

With cron you can have your script run at specific times. Your script would then simply look like this

#!/bin/sh
URL="www.google.com" #This can be changed to whatever you want
FIREFOX="/usr/bin/firefox"
test -x $FIREFOX || exit 1
$FIREFOX $URL

Note that cron is for if you want to the script to run at the same time over and over again. Otherwise actionparsnip's advice about the linux at command is what you should use.

here is an example of that i want to do in MS-Dos it works perfectly but i can't get it do work on ubuntu

at 20:20 firefox http://www4.bux.to/surf.php

at 20:20 firefox http://www4.bux.to/view.php?ad=10350
at 20:21 firefox http://www4.bux.to/view.php?ad=10196
at 20:22 firefox http://www4.bux.to/view.php?ad=10590
at 20:23 firefox http://www4.bux.to/surf.php

at 20:23 firefox http://www4.bux.to/view.php?ad=10736
at 20:24 firefox http://www4.bux.to/view.php?ad=10197

at 20:25 firefox http://www4.bux.to/view.php?ad=10321

The at command works a little bit differently in linux. You want
something that is like this:

 echo "DISPLAY=:0 /usr/bin/firefox www.google.com" | at 01:35

The DISPLAY=:0 is necessary. So if you put a bunch of those into a
shell script and then ran it, all the jobs would be registered and you
should be good to go.