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epoll_wait - wait for an I/O event on an epoll file descriptor
#include <sys/epoll.h> |
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 :
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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.
Tag | Description |
---|---|
EBADF | epfd is not a valid file descriptor. |
EFAULT | The memory area pointed to by events is not accessible with write permissions. |
EINTR | The call was interrupted by a signal handler before any of the requested events occurred or the timeout expired. |
EINVAL | epfd is not an epoll file descriptor, or maxevents 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.
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