Question

I’m trying to check if a particular process is running, and if it is, try and kill it.

I’ve come up with the following so far:

PID=$(ps aux | grep myprocessname | grep -v grep | awk '{print $2}')

if [ -z $PID];
then    
    echo Still running on PID $PID, attempting to kill..
    kill -9 $PID > /dev/null
fi

However when I run this, I get the following output:

kill: usage: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]

What is the best way to kill a running process on unix silently?

Answer 1

[ -z $PID]

is true if $PID is empty, not the other way around, so your test is inverted.

You should be using pgrep if you have that on your system too. (Or even better: pkill and stop worrying about all that shell logic.)