Raspberry GPIO Helper with SYSFS Commands

gpio.sh

#!/bin/sh

#   $1  mode
#   $2  gpio
#   $3  write: value 0/off | 1/on


usage() {
    # command help:
    echo "
### GPIO Helper ###

USAGE: $0 read [gpio]
Read the  gpio

USAGE $0 write [gpio] [value]
Set the GPIO to Value.
Values: off  0  |  on  1
    ";
} # => usage()


set_export() {
    # command set_export:
    if [ ! -d /sys/class/gpio/gpio$1/ ]; then
        echo "$1" > /sys/class/gpio/export
    fi
} # => set_export()


set_direction() {
    # command set_direction:
    if [ "$(cat /sys/class/gpio/gpio$1/direction)" != "$2" ]; then
        echo out > /sys/class/gpio/gpio$1/direction
    fi
} # => set_direction()


read() {
    # command read:
    set_export "$1"
    set_direction "$1" "in"

    sleep 0.2

    cat /sys/class/gpio/gpio$1/value
} # => read()


write() {
    # command write:
    set_export "$1"
    set_direction "$1" "out"

    sleep 0.2
    
    if   [ "$2" = "on" ] || [ "$2" = "1" ]; then
        echo "1" > /sys/class/gpio/gpio$1/value
    elif [ "$2" = "off" ] || [ "$2" = "0" ]; then
        echo "0" > /sys/class/gpio/gpio$1/value
    else
        echo "Invalid argument for write mode"
    fi
} # => write()


# get command name
cmd="$1"

# determine how we were called, then hand off to the function responsible
[ -n "$1" ] && shift # scrape off command
case "$cmd" in
    read)
         read "$@"
        ;;
    write)
         write "$@"
        ;;
    ""|help|-h|--help|--usage)
        usage "$1"
        exit 0
        ;;
    *)
        echo "Unknown command '$cmd'. Run without commands for usage help."
        ;;
esac