信号处理程序停止计时器用C [英] Signal Handler to stop Timer in C

问题描述

我想有一个信号处理程序停止计时，但不退出我的程序。我应该如何着手。我想StopTimer来处理信号，停止计时

I am trying to have a signal handler stop a timer without exiting my program. How should I go about. I want StopTimer to handle the signal to stop the timer

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

#define INTERVAL 2      // number of seconds to go off

int main(int argc, char* argv[]) {

TimerSet(INTERVAL);

while(1)
{
    // do stuff
}
return 0;
}

void TimerSet(int interval)
{
printf("starting timer\n");
struct itimerval it_val;

// interval value
it_val.it_value.tv_sec = interval;
it_val.it_interval = it_val.it_value;

// on SIGALRM, close window
if (signal(SIGALRM, TimerStop) == SIG_ERR)
{
    perror("Unable to catch SIGALRM");
    exit(1);
}

// set interval timer, returns SIGALRM on expiration
if (setitimer(ITIMER_REAL, &it_val, NULL) == -1)
{
    perror("error calling setitimer()");
    exit(1);
}
}

void TimerStop(int signum)
{
printf("Timer ran out! Stopping timer\n");
exit(signum);
}

我试图setitimer函数时间间隔设置为0，但我不知道如何使用相同的计时器TimerStop信号处理函数中

I tried to set the setitimer interval to 0, but I am not sure how to use the same timer within the TimerStop signal handler function

推荐答案

只要设置 it_interval 零，你会得到一个一次性的定时器。你不需要做任何事情在你的处理程序。

Just set it_interval to zero, and you'll get a one-shot timer. You don't need to do anything with it in your handler.

有关实例，在该

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

#define INTERVAL 2              // number of seconds to go off

void TimerStop(int signum) {
    printf("Timer ran out! Stopping timer\n");
}

void TimerSet(int interval) {
    printf("starting timer\n");
    struct itimerval it_val;

    it_val.it_value.tv_sec = interval;
    it_val.it_value.tv_usec = 0;
    it_val.it_interval.tv_sec = 0;
    it_val.it_interval.tv_usec = 0;

    if (signal(SIGALRM, TimerStop) == SIG_ERR) {
        perror("Unable to catch SIGALRM");
        exit(1);
    }
    if (setitimer(ITIMER_REAL, &it_val, NULL) == -1) {
        perror("error calling setitimer()");
        exit(1);
    }
}

int main(int argc, char *argv[]) {

    TimerSet(INTERVAL);

    while (1) {
        // do stuff
    }
    return 0;
}

消息定时跑出来！停止计时器将只出现一次，而你的定时器将停止，没有你做任何事情。

the message "Timer ran out! Stopping timer" will appear only once, and your timer will stop without you doing anything.

请注意，您需要填写您的结构itimerval ，当前您的$ C $的 tv_usec 成员C不这样做。如果你不这样做， it_interval 是极不可能是零，你的计时器将永远不会停止。

Note that you need to fill in the tv_usec members of your struct itimerval, which your current code does not do. If you don't, it_interval is highly unlikely to be zero, and your timer will never stop.

的printf（），与其他标准的IO功能一起，是不是真的安全地从信号处理程序调用，虽然在这种特殊情况下也不会造成你任何问题，因为主要code只是坐在一个循环，并没有做任何事情。

printf(), along with the other standard IO functions, is not really safe to call from a signal handler, although in this particular case it won't cause you any problems, since the main code is just sitting in a loop and not doing anything.

另外，你调用presume 信号（）的宗旨 - 的sigaction（）是设置处理程序推荐的方式。 setitimer函数（）也过时了，现在，和 timer_settime（）推荐。

Also, presume you're calling signal() on purpose - sigaction() is the recommended way for setting handlers. setitimer() is also obsolete, now, and timer_settime() is recommended.

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