Question

我需要在C中运行while循环10秒钟。我尝试过：

clock_t start = clock();

while( ( clock() - start ) < ( 10 * CLOCKS_PER_SEC ) ) {

work..

}

但它不起作用。

Answer 1

请指定什么不起作用。我会猜测：

在Debian 10上，正确的宏为In [198]: np.indices((2,3,4)).sum(axis=0) Out[198]: array([[[0, 1, 2, 3], [1, 2, 3, 4], [2, 3, 4, 5]], [[1, 2, 3, 4], [2, 3, 4, 5], [3, 4, 5, 6]]]) In [199]: idx = np.indices((2,3,4), sparse=True) In [200]: idx Out[200]: (array([[[0]], [[1]]]), array([[[0], [1], [2]]]), array([[[0, 1, 2, 3]]])) In [201]: sum(idx) Out[201]: array([[[0, 1, 2, 3], [1, 2, 3, 4], [2, 3, 4, 5]], [[1, 2, 3, 4], [2, 3, 4, 5], [3, 4, 5, 6]]])。但是也许Ubuntu添加了CLOCKS_PER_SEC作为别名，在这种情况下，这不是您遇到的问题。

实现计时器的方式，循环可能会超过10秒（如果“工作”时间不是10s的除数）。如果这是您的实际问题，则应检查异步任务和信号。这样，您可以让一个进程（或线程）无限循环地进行初始工作，而第二个进程在经过10秒后通知第一个进程（例如，发出信号）。但这将需要更复杂的代码！

希望我能给您带来帮助，但是如果我不尝试更精确地回答您的问题，那么

Answer 2

似乎您真正想要的是一个实际的计时器，以便在经过指定的时间间隔时调用一个函数。在该功能中，您可以处理断开客户端与服务器的连接。

请参阅：https://programming.vip/docs/linux-c-language-timer.html

您应该可以根据需要修改此示例：

#include<stdio.h>
#include<signal.h>
#Include<sys/time.h>//itimerval structure definition

int handle_count=0;
void set_time(void)
{
   struct itimerval itv;
   itv.it_interval.tv_sec=10;//Load automatically and then respond every 10 seconds
   itv.it_interval.tv_usec=0;
   itv.it_value.tv_sec=5;//Time of First Timing
   itv.it_value.tv_usec=0;
   setitimer(ITIMER_REAL,&itv,NULL);
}

void alarm_handle(int sig)
{
   handle_count++;
   printf("have handle count is %d\n",handle_count);
}

void main(void)
{
   struct itimerval itv;
   signal(SIGALRM,alarm_handle);
   set_time();

   while(1){
   getitimer(ITIMER_REAL,&itv);
   printf("pass second is %d\n",(int)itv.it_value.tv_sec);
   sleep(1);
   }

   return;
}

一些手册页链接：

另一个StackOverflow answer的另一个示例：

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <time.h>
#include <unistd.h>

static unsigned int pass_value_by_pointer = 42;

void Timer_has_expired(union sigval timer_data)
{
    printf("Timer expiration handler function; %d\n", *(int *) timer_data.sival_ptr);
}

int main(void)
{
    struct sigevent timer_signal_event;
    timer_t timer;

    struct itimerspec timer_period;

    printf("Create timer\n");
    timer_signal_event.sigev_notify = SIGEV_THREAD;
    timer_signal_event.sigev_notify_function = Timer_has_expired;       // This function will be called when timer expires
    // Note that the following is a union. Assign one or the other (preferably by pointer)
    //timer_signal_event.sigev_value.sival_int = 38;                        // This argument will be passed to the function
    timer_signal_event.sigev_value.sival_ptr = (void *) &pass_value_by_pointer;     // as will this (both in a structure)
    timer_signal_event.sigev_notify_attributes = NULL;
    timer_create(CLOCK_MONOTONIC, &timer_signal_event, &timer);

    printf("Start timer\n");
    timer_period.it_value.tv_sec = 1;                                   // 1 second timer
    timer_period.it_value.tv_nsec = 0;                                  // no nano-seconds
    timer_period.it_interval.tv_sec = 0;                                // non-repeating timer
    timer_period.it_interval.tv_nsec = 0;

    timer_settime(timer, 0, &timer_period, NULL);
    sleep(2);

    printf("----------------------------\n");
    printf("Start timer a second time\n");
    timer_settime(timer, 0, &timer_period, NULL);
    sleep(2);

    printf("----------------------------\n");
    printf("Start timer a third time\n");
    timer_settime(timer, 0, &timer_period, NULL);

    printf("Cancel timer\n");
    timer_delete(timer);
    sleep(2);
    printf("The timer expiration handler function should not have been called\n");

    return EXIT_SUCCESS;
}

运行while循环10秒

2 个答案: