Shell Programming and Scripting

You can't save a password for later that way. sudo, as well as su, ssh, sftp, scp, and most other sane authentication systems, only accept passwords from a terminal, not from a script, as a security feature. There's other options, though.

You could run the entire script under a different user. Not as root -- that's almost never a good idea -- just a different user that sudo won't require a password to /sbin/poweroff with. So you type a password to get into the script and it can do what it needs to from there.

Code:

#!/bin/bash

if [ "$USER" != "scriptuser" ]
then
        # Re-load the script under the appropriate user
        exec sudo -u "scruptuser" "$0" "$@"
fi

...

Or you could run a little loop in sudo that waits for /proc/<shell's pid> to stop existing before running a /sbin/poweroff or /sbin/reboot respectively.

if i understand this correct , you mean let the sudo command check if the converting is done like every 5 minutes so it remembers the password when you entter it at the beginning of the script? or do i misunderstand you?

Yes, you understand me. Not that it runs sudo every 5 minutes -- you run sudo once, and the command it runs checks every few minutes...

and even after hours of converting (lots of movies) it still "remembered" the password

that sounds like the solution i am looking for.
gonna try to let it work, ill get back with the feedback (and propably asking for help )