Shutdown your PC with graphical confirm dialog.

shutdown.sh

#!/bin/bash
# Shutdown the system, with GUI confirm box.
# by Jerry Fleming <jerryfleming2006@gmail.com>,
# on Jun 7, 2013,
# improved on Dec 20, 2013, for systemd compatibility.
# Use at your own risks!

TIME=3 # Three minutes count down.
PATH=$PATH:/sbin # For the shutdown command to be found.
TITLE='Shutdown Confirm'
# This will be interpolated twice, so be careful to quoting.
MSG="\#The system is scheduled to shutdown.\\\nDo you agree?\\\n\\\nYou have \$remain seconds left."

shutdown -h +$TIME &
let TIME*=60
who | awk '
    {
        # If it has a display, not tty or pts.
        if($2 ~ ":"){print $1}
    }
' | while read name
do
    for step in $(seq $TIME)
    do
        remain=$(($TIME-$step))
        eval echo "$MSG"
        echo $(($step*100/$TIME))
        sleep 1
    done | sudo -u $name zenity --progress --title="$TITLE" --percentage=0 2>/dev/null \
    || shutdown -c "Shutdown cancelled by ${name}."
done

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