I edited and commented on your script as to what I edited in does:
Code:
#!/bin/bash
## This prompt will allow you to enter the amount of time you wish for the script to sleep
echo "How long do you wish for the script to sleep:"
## This reads the input as a variable, which will be used to set the amount of time to sleep
read sleep
## The variable is read here
sleep $sleep
killall audacious
You must run this from a terminal, though, as creating a GUI prompt would be getting beyond what Bash can do.
Bookmarks