turtle.refuel() -- might as well, :P

while true do -- loop
 local action = math.random(1,9) -- Random movement generator

 if action == 1 then -- forward
  for i = 1,5 do
   turtle.forward()
  end
 end

 if action == 2 then -- forward
  for i = 1,5 do
   turtle.forward()
  end
 end

 if action == 7 then -- forward
  for i = 1,5 do
   turtle.forward()
  end
 end

 if action == 8 then -- forward
  for i = 1,5 do
   turtle.forward()
  end
 end

 if action == 9 then -- forward
  for i = 1,5 do
   turtle.forward()
  end
 end

 if action == 3 then -- up
  turtle.up()
 end

 if action == 4 then -- down
  turtle.digDown()
  turtle.down()
 end

 if action == 5 then -- left
  turtle.turnLeft()
 end

 if action == 6 then -- right
  turtle.turnRight()
 end
sleep(0.5)
end -- end loop