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GNU/Linux |
CentOS 4.8 |
i386 |
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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 :
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typedef union epoll_data { |
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void *ptr; |
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int fd; |
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__uint32_t u32; |
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__uint64_t u64; |
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} epoll_data_t; |
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struct epoll_event { |
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__uint32_t events; |
/* Epoll events */ | ||||
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epoll_data_t data; |
/* User data variable */ | ||||
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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.
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EBADF |
epfd is not a valid file descriptor. | ||
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EINVAL |
The supplied file descriptor, epfd, is not an epoll file descriptor, or the maxevents parameter is less than or equal to zero. | ||
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EFAULT |
The memory area pointed to by events is not accessible with write permissions. |
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_ctl(2), epoll_create(2), epoll(4)
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epoll_wait(2) | |