Catching user switching and getting current active user from root on linux

[Tim Chase]

On 12/11/2010 01:43 PM, mpnordland wrote:
> it's on linux, and current active user is the user currently
> using the computer. My program needs to switch log files when
> a different user starts using the computer.

The problem is that multiple users can be logged on at the same 
time.  You might be able to come up with a solution that works 
for a small set of use-cases, but I admin several Linux boxes 
where multiple people can be logged-in at the same time.  There 
are also some multi-head arrangements (multiple 
keyboards/mice/monitors and sometimes even sound-cards attached 
to the same motherboard) and people can log into each "terminal" 
(if you will) concurrently, all on the same box.  So if I'm using 
the computer, and a co-worker logs in, I'm still using it at the 
same time you might catch the "new user logged in" event.

Watching wtmp (or possibly /var/log/auth) can capture the "hey, 
somebody logged in" event, but that doesn't mean that other 
previous users are done with their sessions.


-tkc