[ComputerCraft] Goodbye (A Shutdown/Reboot program)

--Centering Text
local function center(text)
  local x,y = term.getSize()
  local x2,y2 = term.getCursorPos()
  term.setCursorPos(math.ceil((x / 2) - (text:len() / 2)), y2)
  write(text)
end

local arg = { ... }

if arg[1] == "-s" then
--Shutdown
  term.setBackgroundColor(colors.lightBlue)
  term.clear()
  center("Shutting Down")
  sleep(1)
  os.shutdown()
elseif arg[1] == "-r" then
--Reboot
  term.setBackgroundColor(colors.lightBlue)
  term.clear()
  center("Rebooting")
  sleep(1)
  os.reboot()
elseif arg[1] == "-h" then
--Help
 print("goodbye -s      SHUTDOWN")
 print("goodbye -r      RESTART")

else
--No args
  error("type \"goodbye -h\" to list arguments")
end