systemd sd_event_get_fd 3 sd_event_get_fd Obtain a file descriptor to poll for event loop events #include <systemd/sd-event.h> int sd_event_get_fd sd_event *event sd_event_get_fd() returns the file descriptor that an event loop object returned by the sd_event_new3 function uses to wait for events. This file descriptor may itself be polled for POLLIN/EPOLLIN events. This makes it possible to embed an sd-event3 event loop into another, possibly foreign, event loop. The returned file descriptor refers to an epoll7 object. It is recommended not to alter it by invoking epoll_ctl2 on it, in order to avoid interference with the event loop's inner logic and assumptions. On success, sd_event_get_fd() returns a non-negative file descriptor. On failure, it returns a negative errno-style error code. Returned errors may indicate the following problems: -EINVAL event is not a valid pointer to an sd_event structure. -ECHILD The event loop has been created in a different process, library or module instance. sd-event3, sd_event_new3, sd_event_wait3, epoll_ctl2, epoll7