For triggering a restart if more than 1 loginwindow process is detected that is not the current logged in user or root after a user logs out

ForceReboot.sh

#!/bin/bash

# Determine loginwindow processes running and reboot the machine if
# more than 1 is detected.

USER=$(/usr/sbin/scutil <<< "show State:/Users/ConsoleUser" | /usr/bin/awk -F': ' '/[[:space:]]+Name[[:space:]]:/ { if ( $2 != "loginwindow" ) { print $2 }}')
# Searches for loginwindow processes and calculates the number running
LOGIN_PROCESSES=$(/usr/bin/pgrep loginwindow)
COUNTLOGINS=$(/bin/echo "$LOGIN_PROCESSES" | /usr/bin/wc -l | /usr/bin/sed 's/ //g')
LOG="/Library/Logs/ForceReboot.log"
P_OWNER=()

writelog () {
	/bin/echo "${1}"
	/bin/echo $(/bin/date) "${1}" >> $LOG
}

# If number of loginwindow process is greater than 1, runs the script
if [ "$COUNTLOGINS" -gt "1" ]; then
	writelog "Multiple logins detected. Running script ..."
else
	writelog "Only 1 user detected. Exiting."
	exit 0
fi

for ((i = 0; i < ${#LOGIN_PROCESSES[@]}; i++)); do
	# Get the loginwindow process owner given the pid and write to array
	P_OWNER+=($(/bin/ps -eo user,pid | /usr/bin/grep -w "${LOGIN_PROCESSES[$i]}" | /usr/bin/awk '{print $1}'))
done

for ((i = 0; i < ${#LOGIN_PROCESSES[@]}; i++)); do
	# If process owner is not the current active user OR root, reboot the machine
	if [ "${P_OWNER[$i]}" != "$USER" ] && [ "${P_OWNER[$i]}" != "root" ]; then
		# Force reboot machine
		writelog "Rebooting to clear logged in user ${P_OWNER[$i]} ..."
		/sbin/shutdown -r now
	fi
done

exit