module-nginx/lib/facter/nginx_version.rb

Facter.add(:nginx_version) do
  setcode do
    if Facter.value('kernel') != 'windows' && Facter::Util::Resolution.which('nginx')
      nginx_version = Facter::Util::Resolution.exec('nginx -v 2>&1')
      %r{nginx version: nginx\/([\w\.]+)}.match(nginx_version)[1]
    end
  end
end