signal信号量如何多次获取

Question

我使用struct sigaction做信号量截获，比如SIGHUP，第一次能收到消息并执行回调函数，但是当第二次收到SIGHUP的时候回调函数并没有执行，是我漏掉了什么清理的地方么？

memset(&sa,0,sizeof(struct sigaction));
    sa.sa_handler = hup_signal;
    sigemptyset(&sa.sa_mask);
    if (sigaction(SIGHUP, &sa, NULL) == -1) {
        printf("sigaction(%d, SIGHUP) failed", SIGHUP);
        return 0;
    }

static void hup_signal(const int sig) {
        printf("get a hup signal %d\n", sig);
    }

Answer 1

可能是你系统版本太旧的缘故？
APUE有过说明 One problem with these early versions is that the action for a signal was reset to its default each time the signal occurred.
所以你可以每次调用处理函数后重新安装一下处理函数，比如

void handler(int signal)
{
  //do whatever
  signal(SIGHUP, handler);
}