Linux Admistration
 

Which commands do you use to output the current users logged into the system and accessing a specific file?

who
this command will list all users logged in on your system.

ps aux | grep <username>
this will list all process by the username you supply

This command (lsof | grep <filename> | cut -c 21-27 | sort -u) will do it. ExampleYou might want to look at info lsof to see what other information is available.

Adminstrative
 

suppose you want to write a shell-script that outputs a periodic listing of owners of files that are active at given times during the day, so as to monitor who was logged in when some particular event occurred e.g when someone changed the contents of files, how would you achieve this ? please help!

I'd use cron to run it (or make the script sleep a certain time, then loop through), and a combination of who and lsof to do the task. I'd probably have a list of files I wanted monitored, either as a text file, or hard-coded in the script, so the lsof would just check those files, or grep for it.

I have merged your two closely-related threads. Please keep one thread per topic---thanks