gimme-xauth.sh

#!/bin/sh
# Script for displaying stuff in the user's screen from ssh without `xhost +`, needs root.
# See comments in http://superuser.com/a/153864/19668 for more details.
#
# Also recommended: something like `export DISPLAY=:0` (and shellinabox for convenience!).
#
# CC-BY Camilo Martin (camilomm.deviantart.com)

# The first parameter is the user. If not supplied, use the current user.
if [ -z "$1" ]; then
    user=$(whoami)
else
    user=$1
fi

# Check if user exists, report if doesn't.
if ! id "$user" > /dev/null 2> /dev/null; then
    echo The user "'$user'" does not even exist.
    return 2
fi

# You'll need root.
for x in $(sudo ls /var/run/gdm3/); do
    gdmuser=$(echo "$x" | grep auth-for-$user-)
    xauth=/var/run/gdm3/$gdmuser/database
done

# Maybe the user is not running X, or GDM.
if [ -z "$gdmuser" ]; then
    echo This user is likely either not running an X server, or is using something else than gdm3.
    return 3
fi

# Export it.
export XAUTHORITY=$xauth

# Done.
echo "\$XAUTHORITY export set, with value '$xauth'"
return 0