Xorg Multi Session Single Monitor: where am I?

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Cagnulein <cagnulein <at> cagnulein.com> writes:

> 
> Scenario:
> - 1 monitor
> - 2 XOrg session (one for user 'a' and another one for user 'b')
> 
> With CTRL-ALT-F7 and CTRL-ALT-F8 I can switch between these 2 virtual 
> sessions.
> But how can I know which session is on the screen? (and so which one is 
> on background?)
> 
> I need this information inside a little daemon running as user 'c' 
> outside XOrg sessions
> 
> Thanks
> Roberto Viola
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> 


I've had My self in similar situation and wasn't able to find any solution on
net, so I've tried to think of "What exactly I want to know?" and came up with
answer: By which of X DISPLAY's physically attached keyboard/mouse is used and
just tried lsof of /dev/input/event* and to my surprise I've hit the spot.
So you can use this string:
ps --no-heading -p `lsof -c /^X$/ 2>&1 | grep event | awk '{ print $2 }' | uniq`
-o command|awk -F: '{ print $2 }'|awk '{ print $1 }'
It is by no means the most elegant solution but it work.
I've made a little demon out of it which update /tmp/CurrentX.DISPLAY,
/tmp/CurrentX.pid and /tmp/CurrentX.tty files accordingly.