分享一段shell脚本--su权限下自动读取某个GPIO电平，判断为低即自动关机的功能

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sudo sh -c "echo 50 > /sys/class/gpio/export"

sudo sh -c "echo "in" > /sys/class/gpio/gpio50/direction"

while(true)
do
gpiovalue=`sudo cat /sys/class/gpio/gpio50/value`
# sleep 3
# echo "gpio:$((gpiovalue))";
if [ "$gpiovalue" = 0 ];
  then
{
echo "shut down system";
shutdown -h now
}
fi
sleep 3
done
sudo sh -c "echo 50 > /sys/class/gpio/unexport"