How to get PID of process by specifying process name and store it in a variable to use further?

If you want to kill -9 based on a string (you might want to try kill first) you can do something like this:

ps axf | grep <process name> | grep -v grep | awk '{print "kill -9 " $1}'

This will show you what you’re about to kill (very, very important) and just pipe it to sh when the time comes to execute:

ps axf | grep <process name> | grep -v grep | awk '{print "kill -9 " $1}' | sh