double gettimeofday_sec()
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
    return tv.tv_sec + (double)tv.tv_usec*1e-6;
}


int main(void) {
	double t1, t2;

	sleep(5);
	printf("hit now");
	t1=gettimeofday_sec();
	getchar();
	t2=gettimeofday_sec();
	printf("time = %10.30f\n", t2 - t1);
	return 0;
}