epoll_wait - 等待在 epoll 文件描述符的I/O事件

内容简介

#include  

int epoll_wait(int epfd, struct epoll_event * events, 
               int maxevents, int timeout); 

描述

Wait for events on the epoll file descriptor epfd for a maximum time of timeoutmilliseconds. 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 makesepoll_wait(2) wait indefinitely, while specifying a timeout equal to zero makesepoll_wait(2) to return immediately even if no events are available (return code equal to zero).

struct epoll_event 的定义如下 :

    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.

返回值

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 timeoutmilliseconds. When an error occurs, epoll_wait(2) returns -1 and errno is set appropriately.

错误

标签	描述
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.

遵循于

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.

另请参阅

• epoll_create (2)

• epoll_ctl (2)