Linux函数学习 epoll

1、Linux epoll函数

1.1、创建epoll实例

int epoll_create1(int flag);

返回值：-1 失败，非负数 成功

flag  ：默认传入0

1.2、管理epoll对象

int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);

epfd  ：epoll 对象文件句柄

op     ：epoll操作动作，添加，修改，删除

fd       ：需要轮询的文件句柄

event  ：需要监听的epoll事件

1.3、等待epoll事件

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

epfd  ：epoll 对象文件句柄

events  ：epoll事件上报

maxevents   ： 最大处理epoll事件数量

timeout ： 超时时间

2、函数实例

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/input.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <string.h>#define MAX_EVENT 1static char * eventTypeToString(__u16 type){switch(type){case EV_SYN:return "EV_SYN";case EV_KEY:return "EV_KEY";case EV_REL:return "EV_REL";case EV_ABS:return "EV_ABS";case EV_MSC:return "EV_MSC";case EV_SW:return "EV_SW";default:return "UNKOWN";}
}static char * eventCodeToString(__u16 code){switch(code){case KEY_ESC:return "KEY_ESC";case KEY_POWER:return "KEY_POWER";default:return "UNKOWN";}
}int main (int argc, char ** argv){int fd; int mEpollFd;int ret;struct input_event event;struct epoll_event ep_event;struct epoll_event pending_event[MAX_EVENT];if(argc != 2){printf("Usage: %s <dev> \n", argv[0]);}fd = open(argv[1], O_RDWR | O_NONBLOCK);if(fd < 0){printf("open %s err \n", argv[1]);} else {printf("open %s success \n",argv[1]);}/*创建EpollFd*/mEpollFd = epoll_create1(0);if(mEpollFd <0){printf("epoll create err = %s \n", strerror(errno));} else {printf("epoll create success \n");}/*添加监听*/ep_event.events = EPOLLIN;ep_event.data.fd = fd;ret = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, &ep_event);if(ret < 0){printf("epoll_ctl err = %s \n", strerror(errno));} else {printf("epoll_ctl success \n");}/*等待文件字符变化*/while(1){ret = epoll_wait(mEpollFd, pending_event, MAX_EVENT, 5);if(ret > 0){if(pending_event[0].data.fd == fd){if (pending_event[0].events & EPOLLIN) {while(read(fd, &event, sizeof(event)) == sizeof(event)){printf("epoll get event: type =0x%x, Code = 0x%x value = 0x%x \n",event.type, event.code, event.value);printf("epoll get event: type = %s, Code = %s value = 0x%x \n",eventTypeToString(event.type), eventCodeToString(event.code), event.value);}}}} else if (ret == 0){//printf("epoll_wait time out \n");} else {perror("epoll_wait error \n");}}return 0;
}

3、代码运行效果

编译二进制文件，运行到手机端