时间函数gettimeofday()

#include <sys/time.h>
struct timeval start,end;
gettimeofday(&start,NULL);
gettimeofday(&end,NULL);

unsigned long duration = 1000*(end.tv_sec-start.tv_sec)+(end.tv_usec-start.tv_usec)/1000;
//sec->second usec->microsecond duration 毫秒格式