list RubyGems that have native extensions

list-native-gems.rb

#!/usr/bin/env ruby 

require 'rubygems'

gempaths = Gem::default_path

puts 
puts "Scanning paths in Gem::default_path for RubyGems with native extensions ..."
puts

gempaths.each do |gempath|
  native_gems = Dir.glob("#{gempath}/gems/**/*.{so,bundle,dylib}").collect { |p| p[/#{Gem::default_path[1]}\/gems\/.*?\//] }.uniq
  puts "#{gempath}/gems: #{native_gems.length} gems with native extensions"
  puts
  unless native_gems.empty?
    native_gems.sort.each do |gem|
      puts "  #{File.basename(gem)}"
    end
    puts
  end
end

output-example.sh

$ /home/sbannasch/src/list-native-gems.rb

Scanning paths in Gem::default_path for RubyGems with native extensions ...

/home/sbannasch/.gem/ruby/1.8: 0 gems with native extensions

/usr/local/lib/ruby/gems/1.8: 59 gems with native extensions

  RedCloth-3.301
  RedCloth-4.0.3
  RedCloth-4.1.1
  RedCloth-4.1.9
  RedCloth-4.2.2
  bcrypt-ruby-2.0.5
  do_sqlite3-0.9.10.1
  em-http-request-0.2.7
  eventmachine-0.12.10
  fastthread-0.6.4.1
  fastthread-1.0.1
  fastthread-1.0
  ffi-0.6.3
  god-0.7.12
  hpricot-0.5.110
  hpricot-0.5
  hpricot-0.6.164
  hpricot-0.6
  johnson-1.2.0
  json-1.0.1
  json-1.1.1
  json-1.1.2
  json-1.1.3
  json-1.2.3
  json-1.4.3
  libxml-ruby-0.5.4
  libxml-ruby-0.6.0
  libxml-ruby-0.7.0
  libxml-ruby-0.8.0
  libxml-ruby-0.9.8
  libxml-ruby-1.1.3
  linecache-0.42
  linecache-0.43
  mongrel-1.0.1
  mongrel-1.1.1
  mongrel-1.1.2
  mongrel-1.1.4
  mongrel-1.1.5
  mysql-2.7
  mysql-2.8.1
  passenger-2.0.6
  passenger-2.1.2
  passenger-2.1.3
  passenger-2.2.15
  passenger-2.2.4
  passenger-3.0.1
  ruby-debug-0.7.5
  ruby-debug-base-0.10.1
  ruby-debug-base-0.10.3
  ruby-debug-base-0.8.1
  ruby-debug-base-0.9.3
  selenium-webdriver-0.0.24
  sqlite3-ruby-1.2.5
  superredcloth-1.160-mswin32
  superredcloth-1.160
  superredcloth-1.163
  superredcloth-1.167
  termios-0.9.4
  thin-1.2.7