ree_gem_migration.rb

def gem_list(bin)
  a = %x(#{bin} list)
  gems = []
  a.each_line do |l|
    gem, *versions = l.gsub(/\(|\)|,/,"").split
    versions.each do |v|
      gems << "#{gem} -v #{v}"
    end
  end
  gems
end

ree_gem_bin = "/opt/ruby-enterprise/bin/ruby /opt/ruby-enterprise/bin/gem"
src_gem_bin = "/usr/bin/gem"
gem_install_cmd = "#{ree_gem_bin} install --no-ri --no-rdoc"

gems = gem_list(src_gem_bin)
already_installed_gems = gem_list(ree_gem_bin)

gems.each do |gem|
  next if already_installed_gems.include?(gem)
  puts "installing #{gem}"
  `sudo #{gem_install_cmd} #{gem}`
end