export_pin_to_filesystem

#!/bin/bash

PIN="${1}"

if [ -z "${PIN}" ]; then
    printf "\nERROR: Missing first argument: pin number\n"
    exit 1
fi

printf "Checking if pin ${PIN} is already exported ... "

PIN_DIR="/sys/class/gpio/gpio${PIN}"
if [ -f "${PIN_DIR}/value" ]; then
    printf "yes\n\n"
else
    printf "no\n\n"

    echo "${PIN}" > /sys/class/gpio/export

    if [ -f "${PIN_DIR}/value" ]; then
        printf "Pin ${PIN} exported to ${PIN_DIR}\n\n"
    else
        printf "ERROR: Failed to export pin ${PIN}"
        exit 1
    fi
fi

VALUE=$(cat "${PIN_DIR}/value")

printf "Pin ${PIN} value = ${VALUE}\n\n"