Question

I have one application and multiple instances of the same application are running in the system. Every instance of the application is invoked with different argument.
I want to get the pid of a particular process which had been invoked with some argument i.e. pid of particular instance of the application according to the argument passed.
Is there any way to get it?

Answer 1

I would probably check output of ps -eo pid,args and grep for the parameters I need and then cut the pid from the beginning of the output:

ps -eo pid,args | grep --parameter=x | cut -c 1-5

Check man page of grep. There are a lot of (somewhat confusing) options that will allow you shape the output of the command. In the above example -e selects all the processes to be shown and -o lets user to choose what to output.