How to loop on gpio?

Question

How can gpio be used to control execution? The following works for showing the input value of gpio63

echo 63 > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio63/direction
cat /sys/class/gpio/gpio63/value

But I've tried a number of things like

while [ /sys/class/gpio/gpio63/value = "1" ]
do 
    sleep 1
done

without success.

Answer 1

You're comparing the string "/sys/class/gpio/gpio63/value" to the string "1". They'll never be equal. If you're looking for a "1" as the content of the file named "/sys/class/gpio/gpio63/value" you should say

while [ "$(cat /sys/class/gpio/gpio64/value)" = 1 ]