do

local tArgs = {...}
if #tArgs <= 1 then
  print( "Usage: do <direction> <distance> ..." )
  return
end

local tHandlers = {
  ["forward"] = turtle.forward,
  ["forwards"] = turtle.forward,
  ["f"] = turtle.forward,
  ["fd"] = turtle.forward,
  ["backward"] = turtle.back,
  ["backwards"] = turtle.back,
  ["bd"] = turtle.back,
  ["b"] = turtle.back,
  ["up"] = turtle.up,
  ["u"] = turtle.up,
  ["down"] = turtle.down,
  ["dn"] = turtle.down,
  ["d"] = turtle.down,
  ["left"] = turtle.turnLeft,
  ["lt"] = turtle.turnLeft,
  ["tl"] = turtle.turnLeft,
  ["l"] = turtle.turnLeft,
  ["right"] = turtle.turnRight,
  ["rt"] = turtle.turnRight,
  ["tr"] = turtle.turnRight,
  ["r"] = turtle.turnRight,
  ["dig"] = turtle.dig,
  ["df"] = turtle.dig,
  ["digdown"] = turtle.digDown,
  ["dd"] = turtle.digDown,
  ["digup"] = turtle.digUp,
  ["du"] = turtle.digUp,
}

local nArg = 1
while nArg <= #tArgs do
    local sDirection = tArgs[nArg]
    local nDistance = 1
    if nArg < #tArgs then
        local num = tonumber( tArgs[nArg + 1] )
        if num then
            nDistance = num
            nArg = nArg + 1
        end
    end
    nArg = nArg + 1

    local fnHandler = tHandlers[string.lower(sDirection)]
    if fnHandler then
        while nDistance > 0 do
            if fnHandler() then
                nDistance = nDistance - 1
            elseif turtle.getFuelLevel() == 0 then
                print( "Out of fuel" )
                return
            else
                sleep(0.5)
            end
        end
    else
        print( "No such direction: "..sDirection )
        print( "Try: forward, back, up, down" )
        return
    end

end