The command "ps" is used to list the processes running in the system and by adding various options to it we can get different informations regarding a process.
To find the time from which a proces has been executing we can use the option etime i.e.
For example, let us createa bash script that will run for 60 seconds
save it and give it execute permissions.
Execute it and put it in the back ground.
Now use the command ps to find the running time of the script.
We can see in the last column that process "script" has been running from 16 seconds.
If we execute ps again after a few secods we can see the change in the value.
Thus we can track the execution times of processes using ps.