install_gems.rb

#!/usr/bin/env ruby
# use this to install the same gems you have installed under one ruby in another
# run "gem list > ~/Desktop/gems.txt"
# run "ruby install_gems.rb /Users/r38y/Desktop/gems.txt"

gems = IO.readlines(ARGV.first)
gems.map! do |g|
  stuff = g.split(' ')
  gem_name = stuff.delete_at(0)
  stuff.map{|v| v.gsub(/[\(\)\,]/, '')}.map{|v| "sudo gem install #{gem_name} -v=#{v}"}
end.flatten!

gems.each do |g|
  puts "running '#{g}'"
  `#{g}`
end