Why can't I kill a process in bash?

Question

I have the following script:

firefox <url>
sleep 5
kill -9 $(pidof firefox)

Thanks in advance

Answer 1

When I run firefox like that on my Linux (Ubuntu 18.04) system the firefox command runs as a foreground process. That means that the sleep 5 command never gets to run.

You need to put the Firefox process into the background like this:

firefox <url> &
sleep 5
kill -9 $(pidof firefox)

It works for me.

Answer 2

You can save the pid in a variable, for a pure shell solution.

firefox <url> & pid=$!
sleep 5
kill "$pid"