gimme_gem.rb

# Small thing for installing gems on-the-fly.
# Useful for "self-contained" scripts, too small to be 
# distributed with own Gemfile & README and stuff.
#
# Usage:
#
#    gimme_gem 'sequel' # Checks OR installs the gem
#    Sequel.connect 'mysql://....'
#
# All credits for managing RubyGems code goes to author
# of this gist: https://gist.github.com/adamjmurray/3154437
def gimme_gem(name, version = nil)
  gem name, version
  require name
rescue Gem::LoadError
  puts "Gem #{name} not found, trying to install..."
  require 'rubygems/commands/install_command'
  args = ["--no-ri", "--no-rdoc", name]
  args.concat(['--version', version]) if version
  Gem::Commands::InstallCommand.new.tap do |c| 
    c.handle_options(args)
    begin
      c.execute 
    rescue Gem::SystemExitException
    end
  end
  require name
end

What about gems which have a different name than the one that needs to be required? Take the awesome_print gem for example, older versions can only be required via require 'ap'

@nilsding Yeah, that is a problem (and Gist doesn't sending comment notifications is another one).