C语言 <time.h> clock 函数

描述

C库函数clock_t clock(void)返回自程序启动以来经过的时钟滴答数。要获得CPU使用的秒数，您需要除以CLOCKS_PER_SEC。在CLOCKS_PER_SEC等于1000000的32位系统上，此函数大约每72分钟将返回相同的值。

声明

以下是clock函数的声明。


clock_t clock(void)

参数

没有参数。

返回值

此函数返回自程序启动以来经过的时钟滴答数。失败时，该函数返回值-1。

示例

以下示例显示clock函数的用法-


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

   return(0);
}

尝试一下

让我们编译并运行上面的程序，它将产生以下结果。


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...