local arg = {...};
    local possibleSides = {"left","right","top","bottom","back","front"};
    local data;
    local mag;

    function checkSide()
      for curSide = 1,6,1 do
        if(arg[2] == possibleSides[curSide]) then
          return true;
        end
      end
      return false;
    end

    function writeCard()
      print("Please swipe your card twice.");
      --local event, side = os.pullEvent("mag_swipe");
      mag.beginWrite(input, arg[1]);
      local event, side = os.pullEvent("mag_swipe");
      mag.cancelWrite();
      print("Writing done!");
      mag.setInsertCardLight(false);
      return true;
    end

    if(arg[1] == nil or arg[2] == nil) then
      print("Usage: writeMAG [label] [side]");
      print("Whereas [label] is the label you want to attach to the card.");
      print("[side] is the side of the Mag Reader");
      return false;
    else
      if(checkSide()) then
        if(peripheral.getType(arg[2]) == "mag card reader") then
          mag = peripheral.wrap(arg[2]);
          print("Please enter card data:");
          input = read("#");
          if not(input == nil) then
            mag.setInsertCardLight(true);
            return writeCard();
          else
            print("Error: Nothing entered.");
          end
        else
          print("That is no mag card reader!");
        end
      else
        print("ERROR: Side " .. arg[2] .. " doesn't exist!");
        return false;
      end
    end