更新时间：2022-01-10 12:15
timeval是一个专业术语。
DESCRIPTION
The functions gettimeofday and settimeofday can get and set the time as
well as a timezone. The tv argument is a timeval struct, as specified
其中tv_usec代表的是微秒（百万分之一秒）精度。
#include
#include
int gettimeofday(struct timeval *tv, struct timezone *tz);
int main(int argc,char * argv[]){
struct timeval tv;
while(1){
gettimeofday(&tv,NULL);
sleep(2);
}
return 0;
}
返回结果为：
evil@dcenter:~/tmp$ ./a.out
time 1142077839:903605
time 1142077841:910129
time 1142077843:920155
time 1142077845:930180
time 1142077847:940205
time 1142077849:950231
time 1142077851:960256
time 1142077853:970280
time 1142077855:980307
time 1142077857:990331
头文件：
timeval
{
time_t tv_sec; //秒 [long int]
suseconds_t tv_usec; //微秒 [long int]
};
成员：
tv_sec
秒
tv_usec
微秒