linux 读取系统时间

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main(void){
struct timespec time_start={0, 0},time_end={0, 0};
clock_gettime(CLOCK_REALTIME, &time_start);
printf("start time %ld,%ld ns\n", time_start.tv_sec, time_start.tv_nsec);
clock_gettime(CLOCK_REALTIME, &time_end);
printf("end   time %lds,%ld ns\n", time_end.tv_sec, time_end.tv_nsec);
printf("duration:%lds %ld ns\n", time_end.tv_sec-time_start.tv_sec, time_end.tv_nsec-time_start.tv_nsec);
return 0;
}