notify-desktop - linux find and notify desktop session

notify-desktop

#!/bin/bash
# Provides a way for a root process to perform a notify send for each
# of the local desktop users on this machine.
#
# Intended for use by cron and timer jobs. Arguments are passed straight
# to notify send.  Falls back to using wall.  Care must be taken to
# avoid using this script in any potential fast loops.
#
# X11 users should already have a dbus address socket at /run/user/<userid>/bus
# and this script should work without requiring any initialisation. Should
# this not be the case, X11 users could initilise a proxy as per the wayland
# instructions below.
#
# Due to stricter security requirements Wayland lacks an dbus socket 
# accessible to root.   Wayland users will need to run a proxy to 
# provide root with the necessary socket.  Each wayland user must add
# the following to a Wayland session startup script:
#
#      notify-desktop --create-dbus-proxy
#
# That will start xdg-dbus-proxy process and make a socket available under:
#      /run/user/<userid>/proxy_dbus_<desktop_sessionid>
#
# Once there is a listening socket, any root script or job can pass
# messages using the syntax of notify-send (man notify-send).
#
# Example messages
#      notify-desktop -a Daily-backup -t 0 -i dialog-information.png "Backup completed without error"
#      notify-desktop -a Remote-rsync -t 6000 -i dialog-warning.png "Remote host not currently on the network"
#      notify-desktop -a Daily-backup -t 0 -i dialog-error.png "Error running backup, please consult journalctl"
#      notify-desktop -a OS-Upgrade -t 0 -i dialog-warning.png "Update in progress, do not shutdown until further completion notice."
#
# Warnings:
#      1) There has only been limited testing on wayland
#      2) There has only been no testing for multiple GUI sessions on one desktop
#

if [ $1 == "--create-dbus-proxy" ]
then
    if [ -n "$DBUS_SESSION_BUS_ADDRESS" ]
    then
        sessionid=$(cat /proc/self/sessionid)
        xdg-dbus-proxy $DBUS_SESSION_BUS_ADDRESS /run/user/$(id -u)/proxy_dbus_$sessionid &
        exit 0
    else
        echo "ERROR: no value for DBUS_SESSION_BUS_ADDRESS environment variable - not a wayland/X11 session?"
        exit 1
    fi
fi


function find_desktop_session {
	for sessionid in $(loginctl list-sessions --no-legend | awk '{ print $1 }')
	do 
		loginctl show-session -p Id -p Name -p User -p State -p Type -p Remote -p Display $sessionid | 
            awk -F= '
                /[A-Za-z]+/ { val[$1] = $2; } 
                END { 
                    if (val["Remote"] == "no" && 
                    val["State"] == "active" && 
                    (val["Type"] == "x11" || val["Type"] == "wayland")) {
                        print val["Name"], val["User"], val["Id"];
                    } 
                }'
	done
}

count=0
while read -r -a desktop_info
do
    if [ ${#desktop_info[@]} -eq 3 ]
    then
        desktop_user=${desktop_info[0]}
        desktop_id=${desktop_info[1]}
        desktop_sessionid=${desktop_info[2]}
        proxy_bus_socket="/run/user/$desktop_id/proxy_dbus_$desktop_sessionid"
        if [ -S $proxy_bus_socket ]
        then
            bus_address="$proxy_bus_socket"
        else
            bus_address="/run/user/$desktop_id/bus"
        fi
        sudo -u $desktop_user DBUS_SESSION_BUS_ADDRESS="unix:path=$bus_address" notify-send "$@" 
        count=$[count + 1]
    fi
done <<<$(find_desktop_session)

# If no one has been notified fall back to wall
if [ $count -eq 0 ]
then
    echo "$@" | wall
fi

# Don't want this to cause a job to stop
exit 0

Some time in the last few weeks passing -t 0 no longer causes a notification to wait forever, rather it disappears immediately without being visible. I find I now have to use -u critical instead of -t 0. I suspect this is due to a change to KDE Plasma.