notify-desktop - linux find and notify desktop session

notify-desktop

#!/usr/bin/env 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 requirments Wayland lacks an dbus socket
# accessable to root.   Wayland users will need to run a proxy to
# provide root with the necessary socket.  Each user can 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

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