# File lib/daemon_controller/lock_file.rb, line 62
        def exclusive_lock
                File.open(@filename, 'w') do |f|
                        if Fcntl.const_defined? :F_SETFD
                                f.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)
                        end
                        f.flock(File::LOCK_EX)
                        yield
                end
        end