[Lubuntu] Notifications to all users in X sessions?

[John Hupp]

I am re-approaching a question I first began chewing on in the thread 
"[Lubuntu] Capture "wall" messages for display on desktop?"

For a Lubuntu LTSP network powered by a UPS, during a power outage I 
want to notify all users in all X sessions with a popup message saying 
that the system is running on battery and about to be shut down.  My 
starting point is the the UPS management daemon runs a control script 
which will call my custom script named "annoyme," and will run that 
script as root.

I have been trying to do this with notify-send, but there is the 
inherent problem that when notify-send is run as root, there is no 
DBUS_SESSION_BUS_ADDRESS variable, and notify-send relies on that value 
to direct its output to the proper session.

There are some scripts that solve the problem for a given user name (see 
below), but I want to address all users in general. Somewhere along the 
line, I thought I saw such a script in passing, but now I can't find it.

I imagine that there is already a developed method for handling a job 
like that, using either notify-send or something else.  Can anyone point 
the way?

------------

And here is an example of a script that addresses one known user:

#!/bin/sh

init_notify() {
     user=`whoami`
     pids=`pgrep -u $user nautilus`
     for pid in $pids; do
         # find DBUS session bus for this session
         DBUS_SESSION_BUS_ADDRESS=`grep -z DBUS_SESSION_BUS_ADDRESS 
/proc/$pid/environ | sed -e 's/DBUS_SESSION_BUS_ADDRESS=//'`
         # use it
         export DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS
     done
}

notify() {
     if [ -z "$DBUS_SESSION_BUS_ADDRESS" ]; then
         init_notify
     fi

     title=$1
     text=$2
     timeout=$3

     if [ -z "$title" ]; then
         return
     fi
     if [ -z "$text" ]; then
         text=$title
     fi
     if [ -z "$timeout" ]; then
         timeout=5000
     fi

     notify-send "$title" "$text" -t $timeout
}

# Just copy&paste these two functions into your script and just type 
'notify "title" "text" 5000' in your script where you want to send a 
notification.
# Don't forget to write the correct username in the "init_notify()" 
function.
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