Originální popis anglicky:
epoll_wait - wait for an I/O event on an epoll file descriptor
Návod, kniha: Linux Programmer's Manual
#include <sys/epoll.h>
int epoll_wait(int epfd
, struct epoll_event * events
, int
maxevents
, int timeout)
Wait for events on the
epoll file descriptor
epfd for a maximum
time of
timeout milliseconds. The memory area pointed to by
events will contain the events that will be available for the caller.
Up to
maxevents are returned by
epoll_wait(2). The
maxevents parameter must be greater than zero. Specifying a
timeout of -1 makes
epoll_wait(2) wait indefinitely, while
specifying a
timeout equal to zero makes
epoll_wait(2) to return
immediately even if no events are available ( return code equal to zero ). The
struct epoll_event is defined as :
typedef union epoll_data {
void *ptr;
int fd;
__uint32_t u32;
__uint64_t u64;
} epoll_data_t;
struct epoll_event {
__uint32_t events; /* Epoll events */
epoll_data_t data; /* User data variable */
};
The
data of each returned structure will contain the same data the user
set with a
epoll_ctl(2)
(EPOLL_CTL_ADD
,EPOLL_CTL_MOD
) while the
events
member will contain the returned event bit field.
When successful,
epoll_wait(2) returns the number of file descriptors
ready for the requested I/O, or zero if no file descriptor became ready during
the requested
timeout milliseconds. When an error occurs,
epoll_wait(2) returns -1 and
errno is set appropriately.
- EBADF
- epfd is not a valid file descriptor.
- EFAULT
- The memory area pointed to by events is not
accessible with write permissions.
- EINVAL
- The supplied file descriptor, epfd, is not an
epoll file descriptor, or the maxevents parameter is less
than or equal to zero.
epoll_wait(2) is a new API introduced in Linux kernel 2.5.44. The
interface should be finalized by Linux kernel 2.5.66.
epoll_create(2),
epoll_ctl(2),
epoll(4)
