def open (file)
    line = file.gets;
    opencells = 0;
    puts "this is reached"
    puts "#{opencells}";
    if line == nil then return end

    # read additional lines

    while line = file.gets do

        # begins with "path", must be path specification
        if line[0...4] == "path"
          p, name, x, y, ds = line.split(/\s/)

        # otherwise must be cell specification (since maze spec must be valid)
        else
            x, y, ds, w = line.split(/\s/,4)
            #puts "cell spec: coordinates (#{x},#{y}) with dirs #{ds}"

            #check if all four walls are open
            check = true;
                if ds.length == 4
                    4.times do |i|
                      case ds[i]
                        when "u", "d", "l", "r"
                            check = true;
                        else
                            check = false;
                      end

                      if check == false
                        break;
                      end
                    end
                end
            if check == true
                opencells = opencells + 1;
            end
        end
    end
  puts "#{opencells}";
end

open(maze_file);