C库函数clock_t clock(void) 返回自该计划推出以来经过的时钟滴答数。秒使用的CPU的数量，您将需要除以CLOCKS_PER_SEC。 

CLOCKS_PER_SEC等于1000000在32位系统中，这个函数将返回相同的值大约每72分钟一次。

声明

以下是clock() 函数的声明。

clock_t clock(void)

参数

• NA

返回值

这个函数返回程序启动以来经过的时钟滴答数。失败时，函数返回值-1。

例子

下面的例子演示了如何使用clock() 函数。

#include <time.h>
#include <stdio.h>

int main()
{
   clock_t start_t, end_t, total_t;
   int i;

   start_t = clock();
   printf("Starting of the program, start_t = %ld
", start_t);
    
   printf("Going to scan a big loop, start_t = %ld
", start_t);
   for(i=0; i< 10000000; i++)
   {
   }
   end_t = clock();
   printf("End of the big loop, end_t = %ld
", end_t);
   
   total_t = (double)(end_t - start_t) / CLOCKS_PER_SEC;
   printf("Total time taken by CPU: %f
", total_t  );
   printf("Exiting of the program...
");

   return(0);
}

让我们编译和运行上面的程序，这将产生以下结果：

Starting of the program, start_t = 0
Going to scan a big loop, start_t = 0
End of the big loop, end_t = 20000
Total time taken by CPU: 0.000000
Exiting of the program...