open('binary', 'wb') do |f|  (0..100).step(10) { |b| f << b.chr }ends = open('binary', 'rb') { |f| f.read } # => "\000\n\024\036(2<FPZd"#---open('binary', 'rb') { |f| f.each_byte { |b| puts b } }# 0# 10# 20# ...# 90# 100#---f = open('binary')f.pos                                                  # => 0f.read(1)                                              # => "\000"f.pos                                                  # => 1#---f.pos = 4                                              # => 4f.read(2)                                              # => "(2"f.pos                                                  # => 6#---f.seek(8)                                    f.pos                                                  # => 8f.seek(-4, File::SEEK_CUR)f.pos                                                  # => 4f.seek(2, File::SEEK_CUR)f.pos                                                  # => 6# Move to the second-to-last byte of the file.f.seek(-2, File::SEEK_END)                                    f.pos                                                  # => 9#---f.read(500)                                            # => "Zd"f.pos                                                  # => 11f.eof?                                                 # => truef.close#---f = open('binary', 'rb+')f.read                                    # => "\000\n\024\036(2<FPZd"          f.pos = 2f.write('Hello.')f.rewindf.read                                    # => "\000\nHello.PZd"f << 'Goodbye.'f.rewindf.read                                    # => "\000\nHello.PZdGoodbye."f.close#---def parse_id3(mp3_file)  fields_and_sizes = [[:track_name, 30], [:artist_name, 30],                       [:album_name, 30], [:year, 4], [:comment, 30],                       [:genre, 1]]  tag = {}  open(mp3_file) do |f|    f.seek(-128, File::SEEK_END)    if f.read(3) == 'TAG' # An ID3 tag is present      fields_and_sizes.each do |field, size|        # Read the field and strip off anything after the first null         # character.        data = f.read(size).gsub(/\000.*/, '')        # Convert the genre string to a number.        data = data[0] if field == :genre        tag[field] = data      end    end  end  return tagendparse_id3('ID3.mp3')# => {:year=>"2005", :artist_name=>"The ID Three", #     :album_name=>"Binary Brain Death", #     :comment=>"http://www.example.com/id3/", :genre=>22, #     :track_name=>"ID 3"}parse_id3('Too Indie For ID3 Tags.mp3')         # => {}#---#Returns [track, artist, album, year, comment, genre]def parse_id3(mp3_file)  format = 'Z30Z30Z30Z4Z30C'  open(mp3_file) do |f|    f.seek(-128, File::SEEK_END)    if f.read(3) == "TAG" # An ID3 tag is present      return f.read(125).unpack(format)    end  end  return nilendparse_id3('ID3.mp3')# => ["ID 3", "The ID Three", "Binary Brain Death", "2005", "http://www.example.com/id3/", 22]#---id3 = ["ID 3", "The ID Three", "Binary Brain Death", "2005",        "http://www.example.com/id3/", 22]id3.pack 'Z30Z30Z30Z4Z30C'# => "ID 3\000\000\000\000\000...http://www.example.com/id3/\000\000\000\026"#---