gistfile1.rb

gems = %x[gem list --local 2>/dev/null]
installed_gems = {}

gems.each do |g|
  gem, versions = g.split(' ',2)
  installed_gems[gem] = versions.scan(/[\w\.]+/)
end

installed_gems.each do |gem,versions|
  versions.each do |version|
    puts "gem install #{gem} -v=#{version}"
  end
end