#include <sys/epoll.h>
int epoll_create(int size);
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);
int epoll_wait(int epfd, struct epoll_event *events,int maxevents, int timeout);

op

说明

EPOLL_CTL_ADD

注册目标文件描述符fd到epoll实例，并关联事件event

EPOLL_CTL_MOD

改变关联到目标文件描述符fd的事件event

EPOLL_CTL_DEL

从epoll实例移除目标文件描述符，event被忽略，可以是NULL

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 */
};

events

说明

EPOLLIN

关联的文件可以进行read(2)操作

EPOLLOUT

关联的文件可以进行write(2)操作

EPOLLRDHUP

(since Linux 2.6.17)

对方关闭了流套接字连接，or shut down writing half of connection。

EPOLLPRI

有紧急数据可以进行read(2)操作

EPOLLERR

在关联的文件描述上发生了错误，epoll_wait(2)总会等待这一事件，因此无需对此位置位

EPOLLHUP

关联的文件描述符挂起（Hang up）了，poll_wait(2)总会等待这一事件，因此无需对此位置位

EPOLLET

为关联的文件描述符设置边沿触发，默认的行为是电平触发（Level Triggered）

EPOLLONESHOT

(since Linux 2.6.2)

为关联的文件描述符设置单次行为，这意味着该文件描述符一旦由epoll_wait(2)返回一次事件，就会被内部失能，再不会有其他事件被报告，用户程序必须调用epoll_ctl()函数，使用EPOLL_CTL_MOD命令重新关联event

#include <sys/epoll.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
    int epoll_fd;
    int fds_num;
    char str[50]={0};
    struct epoll_event ev_in,ev_out;
    fds_num = 0;

    epoll_fd = epoll_create(2); /*this ‘size‘ argument is ignored*/
    if (-1 == epoll_fd){
        perror("epoll_create");
        return -1;
    }
    memset(&ev_in, 0, sizeof (ev_in));
    memset(&ev_out, 0, sizeof (ev_out));
    ev_in.events = EPOLLIN;
    if (-1 == epoll_ctl(epoll_fd, EPOLL_CTL_ADD, 0, &ev_in)){/*Register the target file descriptor 0,that is stdin*/
        perror("epoll_ctl");
        return -1;
    }

#define TIMEOUT 20
    while(1){
        fds_num = epoll_wait(epoll_fd, &ev_out, 5, TIMEOUT*1000);
        //fds_num = epoll_wait(epoll_fd, &ev_out, 5, -1);
        if (-1 == fds_num){
            perror("epoll_wait");
            return -1;
        }else if (0 == fds_num){
            printf("none data within %u s\n",TIMEOUT);
            return 0;
        }
        if ( 0 == ev_out.data.fd){
            if ((ev_out.events & EPOLLIN) != 0){
                //printf("events is %x\n",ev_out.events);
                if (-1 == read(0, str, 50)){
                    perror("read");
                    return -1;
                }
                printf("%s",str);
                memset(str, 0 ,sizeof (str));
            }
        }else{
            printf("%d\n",ev_out.data.fd);
        }
    }
    return 0;
}