C代码计时

#include 
#include 

static timespec diff(timespec start, timespec end){
	timespec temp;
	if ((end.tv_nsec - start.tv_nsec) < 0 ){
		temp.tv_sec = end.tv_sec - start.tv_sec - 1 ;
		temp.tv_nsec = 1000000000 + end.tv_nsec - start.tv_nsec;
	} else {
		temp.tv_sec = end.tv_sec - start.tv_sec;
		temp.tv_nsec = end.tv_nsec - start.tv_nsec;
	}
	return temp;
}

int main(){
	int i, temp;
	timespec diff, time1, time2;
	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1);
    temp = 1;
	for(i = 0 ;i < 242000000 ; ++i)
		temp += temp;
	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time2);
	printf("%d:%dn", diff.tv_sec, diff.tv_nsec);
	getchar();
	return 0 ;
}