EPOLL_WAIT(3C) Standard C Library Functions EPOLL_WAIT(3C)

epoll_wait, epoll_pwait - wait for epoll events

#include <sys/epoll.h>
int epoll_wait(int epfd, struct epoll_event *events,
     int maxevents, int timeout);

int epoll_pwait(int epfd, struct epoll_event *events,
     int maxevents, int timeout,
     const sigset_t *sigmask);

The epoll_wait() function waits for events on the epoll(5) instance specified by epfd. The events parameter must point to an array of maxevents epoll_event structures to be filled in with pending events. The timeout argument specifies the number of milliseconds to wait for an event if none is pending. A timeout of -1 denotes an infinite timeout.

The epoll_pwait() is similar to epoll_wait(), but takes an additional sigmask argument that specifies the desired signal mask when epoll_pwait() is blocked. It is equivalent to atomically setting the signal mask, calling epoll_wait(), and restoring the signal mask upon return, and is therefore similar to the relationship between select(3C) and pselect(3C).

Upon successful completion, epoll_wait() and epoll_pwait() return the number of events, or 0 if none was pending and timeout milliseconds elapsed. If an error occurs, -1 is returned and errno is set to indicate the error.

The epoll_wait() and epoll_pwait() functions will fail if:


epfd is not a valid file descriptor.


The memory associated with events was not mapped or was not writable.


A signal was received during the epoll_wait() or epoll_pwait().


Either epfd is not a valid epoll(5) instance or maxevents is not greater than zero.

The epoll(5) facility is implemented for purposes of offering compatibility for Linux-borne applications; native applications should continue to prefer using event ports via the port_create(3C), port_associate(3C) and port_get(3C) interfaces. See epoll(5) for compatibility details and restrictions.

epoll_create(3C), epoll_ctl(3C), port_create(3C), port_associate(3C), port_get(3C), pselect(3C), epoll(5)
April 17, 2014