# File src/ruby_supportlib/phusion_passenger/platform_info/apache.rb, line 466
    def self.apu_config
      if env_defined?('APU_CONFIG')
        return ENV['APU_CONFIG']
      elsif apxs2.nil?
        return nil
      else
        filename = `#{apxs2} -q APU_CONFIG 2>/dev/null`.strip
        if filename.empty?
          apu_bindir = `#{apxs2} -q APU_BINDIR 2>/dev/null`.strip
          if apu_bindir.empty?
            return nil
          else
            return select_executable(apu_bindir,
              "apu-1-config", "apu-config")
          end
        elsif File.exist?(filename)
          return filename
        else
          return nil
        end
      end
    end