export GPIO_PIN_NUMBER=638 # corresponds to /dev/gpiochip2, line index 10

echo $GPIO_PIN_NUMBER > /sys/class/gpio/export

trap "echo $GPIO_PIN_NUMBER > /sys/class/gpio/unexport" EXIT 

echo "EXPORTED PIN ${GPIO_PIN_NUMBER}: "
ls /sys/class/gpio

echo "SETTING MODE TO OUTPUT"
echo 'out' > /sys/class/gpio/gpio${GPIO_PIN_NUMBER}/direction

while true; do
    echo "SETTING VALUE TO 1"
    echo 1 > /sys/class/gpio/gpio${GPIO_PIN_NUMBER}/value
    echo "VALUE IS: " $(cat /sys/class/gpio/gpio${GPIO_PIN_NUMBER}/value)
    sleep 5

    echo "SETTING VALUE TO 0"
    echo 0 > /sys/class/gpio/gpio${GPIO_PIN_NUMBER}/value
    echo "VALUE IS: " $(cat /sys/class/gpio/gpio${GPIO_PIN_NUMBER}/value)
    sleep 5
done