big_shuffle.rb

line_starts = []

filename = "/usr/share/dict/words"

# preprocess
File.open(filename, "r") do |input|
  until input.eof?
    pos = input.pos
    input.readline
    line_starts << pos
  end
end

# random sort, retrieve from file
line_starts.shuffle!
File.open(filename, "r") do |input|
  until line_starts.empty?
    input.seek(line_starts.shift)
    puts input.readline
  end
end