C中的多个警报? [英] Multiple alarms in C?

问题描述

这可能是一个非常基本的问题，但我正在使用下面的代码来运行一个简单的警报.它按我的意愿工作，但我想知道是否有可能同时运行多个警报，每个警报在完成时触发不同的功能.有没有办法做到这一点?

This is probably a very basic question, but I'm using the code below to run a simple alarm. It works as I want it to, but I'm wondering if it's at all possible to run multiple alarms simultaneously that each trigger a different function when complete. Is there a way to do that?

#include <signal.h>
#include <sys/time.h>
#include <stdio.h>
#include <time.h>

void alarm_handler(int signum){
    printf("five seconds passed!!\n");
}
int main(){
    signal(SIGALRM, alarm_handler);
    alarm(5);

    pause();
    return 0;
}

推荐答案

不使用 alarm(2)，但是，您可以使用 POSIX 计时器来实现您的目标.

Not with alarm(2), however, you can use POSIX timers to achieve your goal.

您可以设置每个计时器在到期时运行不同的信号，或者您可以使用单个信号并通过 siginfo_t 将指针传递给计时器，然后您可以根据它来决定在处理程序中做什么.

Either you can set each timer to run a different signal when it expires or you can use a single signal and pass a pointer to the timer with it via siginfo_t, based on which you can then decide what to do in the handler.

示例:

#include <signal.h>
#include <stdio.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>

static timer_t tmid0, tmid1;

static void hndlr(int Sig, siginfo_t *Info, void *Ptr)
{
    if(Info->si_value.sival_ptr == &tmid0)
        write(2, "tmid0\n", 6);
    else{
        write(2, "tmid1\n", 6);
        _exit(0);
    }
}


int main()
{
    int r = EXIT_SUCCESS;

    sigaction(SIGALRM, &(struct sigaction){ .sa_sigaction = hndlr, .sa_flags=SA_SIGINFO }, 0);
    printf("%p %p\n", (void*)&tmid0, (void*)&tmid1);

    struct sigevent sev = { .sigev_notify = SIGEV_SIGNAL, .sigev_signo = SIGALRM };

    sev.sigev_value.sival_ptr = &tmid0; 
    if(0>timer_create(CLOCK_REALTIME,&sev,&tmid0))
        { r=EXIT_FAILURE; goto out; }

    sev.sigev_value.sival_ptr = &tmid1; 
    if(0>timer_create(CLOCK_REALTIME,&sev,&tmid1))
        { r=EXIT_FAILURE; goto out; }

    if(0>timer_settime(tmid0, 0, &(struct  itimerspec const){ .it_value={1,0} } , NULL) )
        { r=EXIT_FAILURE; goto out; }
     //tmid0 expires after 1 second

    if(0>timer_settime(tmid1, 0, &(struct  itimerspec const){ .it_value={3,0} } , NULL) )
        { r=EXIT_FAILURE; goto out; }
     //tmid1 expires after 3 seconds


    for(;;)
        pause();

out:
    if(r)
        perror(0); 
    return r;
}

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