x::timerfd is a reference to a reference-counted object that implements the Linux kernel timer file descriptor API (the timerfd_create(2), timerfd_settime(2), and timerfd_gettime(2) system calls). See the reference documentation for more information on using the timer file descriptor.

The timer file descriptor inherits from the file descriptor object. It is safe to use the following methods from the underlying file descriptor object: epoll() (allowing the file descriptor object to be used in an epoll set), closeonexec(), nonblock(), and get_fd(). Using other methods is discouraged, to avoid unintended side-effects.