bench.rb

require 'benchmark'

Dir.mkdir('results') unless File.exists?('results')
$stdout = File.new("results/#{Process.pid}.txt", 'w')

puts "Start: #{Time.now.strftime('%H:%M:%S')}"

array = (1..1000000).map { rand }; nil

Benchmark.bmbm do |x|
  x.report('sort!') { array.dup.sort! }
  x.report('sort')  { array.dup.sort  }
end

puts "Finish: #{Time.now.strftime('%H:%M:%S')}"

multi.sh

echo Running $1 times...

for ((i = 1; i <= $1; i++)) do
  ruby bench.rb &
done