#! /bin/bash

echo "20" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio20/direction
echo "1" > /sys/class/gpio/gpio20/value
echo "21" > /sys/class/gpio/export
echo "in" > /sys/class/gpio/gpio21/direction

while ( true )
do
if [ $(</sys/class/gpio/gpio21/value) == 1 ]
then
echo "20" > /sys/class/gpio/unexport
echo "21" > /sys/class/gpio/unexport
shutdown -P now
fi
sleep 1
done