libevent_study/test_file/test_file.cpp

#include <iostream>
#include <event2/event.h>
#include <string.h>
#include <thread>

#ifdef _WIN32
	
#else
	#include <signal.h>
    
    #include <unistd.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
#endif // !_WIN32

using namespace std;

void read_file(evutil_socket_t fd,short event,void *arg){
    char buf[1024] = {0};
    int len = read(fd,buf,sizeof(buf) - 1);
    if(len > 0){
        cout << buf << endl;  // 当有用户登录就会把 该信息打印出来 
    }else {
        cout << "." << endl;    
        this_thread::sleep_for(500ms);
    }
    
}

int main(int agrc,char** agrv){
#ifdef _WIN32
	//初始化socket库
	WSADATA wsa;
	WSAStartup(MAKEWORD(2, 2), &wsa);
#else 
	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) { //忽略管道信号，发送数据给已关闭的socket，会飞掉！
		return 1;
	}
#endif

    event_config* conf = event_config_new();
    event_config_require_features(conf,EV_FEATURE_FDS);
    event_base *base = event_base_new_with_config(conf);
    event_config_free(conf);

    if(!base){
        cerr << "event_base_new_with_config failed" <<endl;
    }
    int sock = open("/var/log/auth.log",O_RDONLY|O_NONBLOCK,0);
    if(sock < 0){
        cerr << "/var/log/auth.log open failde" << endl; 
    }

    lseek(sock,0,SEEK_END);

    //监听文件数据
    event* fev = event_new(base,sock,EV_READ|EV_PERSIST ,read_file,0);
    event_add(fev,NULL);
    
    //进入事件主循环
    event_base_dispatch(base);
    event_free(fev);
    event_base_free(base);
   
    return 0;

}