linux command
 

how can i find the owner of jobs that have been executed already not currently running ones
using ps tells me the currently running jobs ,
but how do i find jobs that are already executed and its user

The kernel doesn't track completed processes (except for zombies, but they're usually cleaned up).

that's right... but i'm sure you could find some third party software to log all programs as they are run. or eve write a script (or cron job) to do the following
ps -ef >> log.txt

Check out the documentation for your system logger. If you are already using one of the more advanced loggers (like metalog or syslog-ng) I think it should be pretty easy to process execution info dumped to a log file. Just beware, there is potentially going to be a TON of data there.