Pi Supply Switch v1.1 bash SoftShut script

#!/bin/bash

echo "4" > /sys/class/gpio/unexport

echo "4" > /sys/class/gpio/export
echo "in" > /sys/class/gpio/gpio4/direction

val=`cat /sys/class/gpio/gpio4/value`
while [ $val = 0 ]; do
  sleep 0.1;
  val=`cat /sys/class/gpio/gpio4/value`
done

shutdown -h now