    # File lib/phusion_passenger/platform_info/apache.rb, line 123
            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