GNU/Linux man pages
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GNU/Linux |
CentOS 5.3 |
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epoll_wait(2) |
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epoll_wait − wait for an I/O event on an epoll file descriptor
#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.
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EBADF |
epfd is not a valid file descriptor. | ||
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EFAULT |
The memory area pointed to by events is not accessible with write permissions. | ||
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EINTR |
The call was interrupted by a signal handler before any of the requested events occurred or the timeout expired. | ||
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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.
epoll_create(2), epoll_ctl(2), epoll(7)
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epoll_wait(2) | |