Linux – How to write a shell script to find PID and Kill

I’m trying to write a script to find the PID of another script I ran earlier. Once the PID is found, it sends a stop signal.

I

can find the PID but the kill signal is not processed and I get a return message saying it’s not a PID.

Here’s what I’m doing :

#!/bin/bash   
 PID=`ps -eaf | grep "start.sh" | awk '{print $2}'`
    echo "$PID"    
    if [[ -z "$PID" ]];
     then(
            echo "Start script is not running!"
    )else(
            kill -9 $PID
    )fi

The script it tries to kill starts many others, so I hope killing start.sh will kill all child processes.

When you run

ps -eaf | grep "start.sh" | awk '{print $2}'

You create a subshell that contains the word start.sh. grep will then start its own process and start.sh process, which will give you two PIDs.

This means when you try to kill start.sh and

ps -eaf | grep "start.sh" | awk '{print $2}'

Process. start.sh will die, but the other will no longer exist and therefore cannot be killed, so it gives you an error.

If you’re splitting commands, you’ll probably have better luck:

PIDS=$(ps -eaf)
PID=$(echo "$PIDS" | grep "start.sh" | awk '{print $2}')