Linux Command

To see currently running process $ ps
To stop any process by PID i.e. to kill process
kill {PID} $ kill 1012
To get information about all running process ps -ag $ ps -ag
To display the owner of the processes along with the processes ps aux $ ps aux

To see if a particular process is running or not. For this purpose you have to use ps command in combination with the grep command

For e.g. you want to see whether Apache web server process is running or not then give command

$ ps ax | grep httpd

To see currently running processes and other information like memory and CPU usage with real time updates. top
See the output of top command.
$ top