Printer power shell script

printer_power

#!/bin/bash

pins=(13 19 20 21)
default_power_state=1
usb_hub=0
usb_port=2

init () {
  for pin in ${pins[@]}; do
    echo ${pin} > /sys/class/gpio/export
    echo "out" > /sys/class/gpio/gpio${pin}/direction
  done
}

power () {
  relay_power
  usb_power
}

relay_power () {
  for pin in ${pins[@]}; do
    echo ${power_state} > /sys/class/gpio/gpio${pin}/value
  done
}

usb_power () {
  hub-ctrl -h ${usb_hub} -P ${usb_port} -p ${power_state}
}

usage () {
  echo "usage:  power_relay action"
  echo "  actions:"
  echo "    init: initializes gpio and set to default power state (currently ${default_power_state})"
  echo "    on: turns power on"
  echo "    off: turns power off"
}

if [ -z $1 ] ; then
  usage
  exit
fi

if [ $1 != 'init' -a $1 != 'on' -a $1 != 'off' ]; then
  usage
  exit
fi

if [ $1 == 'init' ]; then
  init
  power_state=${default_power_state}
  power
  exit
fi

if [ $1 == 'on' ]; then
  power_state=1
  power
  exit
fi

if [ $1 == 'off' ]; then
  power_state=0
  power
  exit
fi