How do I see the list of files open in a directory by other users? I can do "lsof +D", but that only shows current user's files. Any way to see if other users have opened files in a directory?
You can't unless you are performing this as root.
If you wanted, you can setup an sudo alias for lsof, but it would either be very generic (i.e. this user can see the whole lsof output) or very specific (this user can only see this other user's lsof -u user output).