How should I determine if a user is logged in graphically while lightdm is running?

Question

I want to know if someone is logged into a local X-session. In the past I looked at the output of ck-list-sessions. The output looked something like this:

Session12:
    unix-user = '[redacted]'
    realname = '[redacted]'
    seat = 'Seat1'
    session-type = ''
    active = TRUE
    x11-display = ':0'
    x11-display-device = '/dev/tty8'
    display-device = ''
    remote-host-name = ''
    is-local = TRUE
    on-since = '2012-10-22T18:17:55.553236Z'
    login-session-id = '4294967295'

If no one was logged in, there was no output. I checked if someone was logged in with

ck_result" string => execresult("/usr/bin/ck-list-sessions | /bin/grep x11 | /usr/bin/cut --delimiter=\\' -f 2 | /usr/bin/wc -w

This no longer works, because lightdm greeter looks like a logged in user

Session12:
    unix-user = '[redacted]'
    realname = 'Light Display Manager'
    seat = 'Seat1'
    session-type = 'LoginWindow'
    active = TRUE
    x11-display = ':0'
    x11-display-device = '/dev/tty8'
    display-device = ''
    remote-host-name = ''
    is-local = TRUE
    on-since = '2012-10-22T22:17:55.553236Z'
    login-session-id = '4294967295'

I guess I could check session-type, but I don't know how to do that and check x11-display in one-liner. I then need to write my own script, but at that point I thought I would check if anyone else has already done the work or if there is a way to get ConsoleKit to tell me what I want (or if I should be using a different tool)?

Answer 1

See the answer to this question. You will probably end up using D-Bus and ConsoleKit.

Answer 2

As it happens, I just needed to solve this - but the best I've managed is 'nasty hack'-esque code:

dbus-send --system --type=method_call --print-reply=literal --dest=org.freedesktop.ConsoleKit `dbus-send --system --type=method_call --print-reply=literal --dest=org.freedesktop.ConsoleKit /org/freedesktop/ConsoleKit/Seat1 org.freedesktop.ConsoleKit.Seat.GetActiveSession` org.freedesktop.ConsoleKit.Session.GetX11Display | grep ":" &&  dbus-send --system --type=method_call --print-reply=literal --dest=org.freedesktop.ConsoleKit `dbus-send --system --type=method_call --print-reply=literal --dest=org.freedesktop.ConsoleKit /org/freedesktop/ConsoleKit/Seat1 org.freedesktop.ConsoleKit.Seat.GetActiveSession` org.freedesktop.ConsoleKit.Session.GetUnixUser | grep -v "uint32 122$" && echo "Active User"

I believe the uid of lightdm is consistent across Ubuntu installs, but this would need adjustment for other display managers.

The code checks:

1. Does the active physical seat have an X Display?
2. If it does, does its uid match 122 (lightdm)?
3. You end up with output of the X display, the users uid, and could execute arbitrary success code script of echo "Active User".