libevent（五）监控linux系统日志文件

文章目录

#include <iostream>
#include <event2/event.h>
#include <thread>
#ifndef _WIN32
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#endif
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;
  }
  else
  {
    cout << "..." << endl;
    this_thread::sleep_for(500ms);
  }

}

int main(int argc, char** argv) {
#if _WIN32
  //windowns 初始化socket库
  WSADATA wsa;
  WSAStartup(MAKEWORD(2, 2), &wsa);
#else
  //linux 忽略管道信号，发送数据给已关闭的socket
  if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
    return 1;
#endif
  event_config* cfg = event_config_new();
  event_config_require_features(cfg, EV_FEATURE_FDS);
  event_base* base = event_base_new_with_config(cfg);
  if (!base)
  {
    cout << "event_base_new_with_config failed!" << endl;
    return -1;
  }

  //打开文件只读，非阻塞
  int sock = open("/var/log/auth.log", O_RDONLY | O_NONBLOCK, 0);
  if (sock<=0)
  {
    cout << "open /var/log/auth.log failed!" << endl;
    return -2;
  }
  
  //文件指针移到结尾处
  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);



  event_config_free(cfg);

  //进入事件主循环
  event_base_dispatch(base);
  event_base_free(base);
#ifdef _WIN32
  WSACleanup();
#endif // _WIN32
  return 0;
}

Makefile

test_file:test_file.cpp
        g++ $^ -o $@ -levent
        ./$@

运行程序时，另开session登录，出现日志输出：