Control the LEDs on a Raspberry Pi

led_control.sh

#! /bin/bash
# led_control [on|off] : Turn the LEDs on or off

function display_usage() {
        echo "Control the Raspberry Pi leds"
        echo -e "\nUsage:\n$0 [on|off]\n"
        exit 1
}
[ $# -eq 0 ] && display_usage

[ "$1" = "on" ] && value=255 || { [ "$1" = "off" ] && value=0 || display_usage; }

printf "Turning leds %s\n" $(awk '{print toupper($0)}' <<< $1)
for led in /sys/class/leds/led*; do
	echo $value | sudo tee -a ${led}/brightness > /dev/null
done
unset led
unset value