module Enumerable
def random_line
selected = nil
each_with_index { |line, lineno| selected = line if rand < 1.0/lineno }
return selected.chomp if selected
end
end
# Create a file with 1000 lines
open('random_line_test', 'w') do |f|
1000.times { |i| f.puts "Line #{i}" }
end
# Pick random lines from the file.
f = open('random_line_test')
f.random_line # => "Line 520"
f.random_line # => nil
f.rewind
f.random_line # => "Line 727"