# File src/ruby_supportlib/phusion_passenger/platform_info/apache.rb, line 91
    def self.httpd_version(options = nil)
      if options
        httpd = options[:httpd] || self.httpd(options)
      else
        httpd = self.httpd
      end
      if httpd
        `#{httpd} -v` =~ %r{Apache/([\d\.]+)}
        return $1
      else
        return nil
      end
    end