def size(filename)
      with_binary(true) do
        resp = sendcmd("SIZE " + filename)
        if resp[0, 3] != "213"
          raise FTPReplyError, resp
        end
        return resp[3..-1].strip.to_i
      end
    end
def size(filename)
      with_binary(true) do
        resp = sendcmd("SIZE " + filename)
        if resp[0, 3] != "213"
          raise FTPReplyError, resp
        end
        return resp[3..-1].strip.to_i
      end
    end
Returns the size of the given (remote) filename.