C++ 后台进程 daemon

bool Switcher::Daemon() {
  base::YamlConfig config;
  if (!config_.ReadConfig(config_file_)) {
    fprintf(stderr, "read config file fail.\n");
    return false;
  }
  bool is_daemon = config_.Get<bool>(kService, "is_daemon");
  if (!is_daemon) {
    return true;
  }
  if (fork() != ) {
    exit();
  }
  setsid();
  if (fork() != ) {
    exit();
  }

  close();
  close();
  close();
  open("/dev/null", O_RDWR);
  dup();
  dup();

  std::string stdout_log_path;
  if(config_.Get<std::string>(kService, kStdoutLogPath, &stdout_log_path)) {
    string filename = stdout_log_path + "." + DateString_();
    int fd = open(filename.c_str(), O_WRONLY | O_APPEND | O_CREAT, );
    if (fd != -) {
      // 将STDOUT, STDERROR 重定向到文件
      dup2(fd, STDOUT_FILENO);
      dup2(fd, STDERR_FILENO);
      close(fd);
    }
  }

  return true;
}