#include 
     
            /* puts, printf */#include 
      
              /* time_t, struct tm, time, localtime */int main (){    struct tm * timeinfo;    double seconds;    time_t start_time,now;        time (&start_time);        while(1){        time (&now);        seconds = difftime(now,start_time);        if(seconds==5){            break;        }    }        timeinfo = localtime (&start_time);    printf ("start_time local time and date: %s", asctime(timeinfo));    timeinfo = localtime (&now);    printf ("now local time and date: %s", asctime(timeinfo));        printf("time spend %f\n",seconds);    return 0;}
      
     

输出

start_time local time and date: Fri May 24 10:24:40 2019now local time and date: Fri May 24 10:24:45 2019time spend 5.000000