怎样知道程序运行消耗的时间

 #include<stdio.h>
 #include<stdlib.h>
 #include<string.h>
 #include"time.h"
 #define inf 100000000
 #define CLOCKS_PER_SEC ((clock_t)1000)
 int main()//注意是int
 {
     double duration;
     clock_t start,finish;
     start=clock();

  /*这里是主程序的代码*/

     finish=clock();
     duration=(double)(finish-start)/CLOCKS_PER_SEC;
     printf("%lf seconds/n",duration);
     return 0;
 }