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此博客展示了一段C语言代码，用于获取当前时间并精确到微秒。代码中定义了多个常量，通过`gettimeofday`函数获取时间，经过一系列计算，将时间转换为年、月、日、时、分、秒和毫秒的格式，并最终输出。

#include <stdio.h>
#include <string.h>
#include <sys/time.h>

#define BEIJINGTIME 8
#define DAY        (60*60*24)
#define YEARFIRST 2001
#define YEARSTART (365*(YEARFIRST-1970) + 8)
#define YEAR400    (365*4*100 + (4*(100/4 - 1) + 1))
#define YEAR100    (365*100 + (100/4 - 1))
#define YEAR004    (365*4 + 1)
#define YEAR001    365

取当前时间，精确到微秒；

int main(int argc, char *argv[])
{
struct timeval tv;

    long sec = 0, usec = 0;
    int yy = 0, mm = 0, dd = 0, hh = 0, mi = 0, ss = 0, ms = 0;
    int ad = 0;
    int y400 = 0, y100 = 0, y004 = 0, y001 = 0;
    int m[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    int i;

memset(&tv, 0, sizeof(timeval));

gettimeofday(&tv, NULL);

    sec = tv.tv_sec;
    usec = tv.tv_usec;
    sec = sec + (60*60)*BEIJINGTIME;

ad = sec/DAY;

    ad = ad - YEARSTART;
    y400 = ad/YEAR400;
    y100 = (ad - y400*YEAR400)/YEAR100;
    y004 = (ad - y400*YEAR400 - y100*YEAR100)/YEAR004;
    y001 = (ad - y400*YEAR400 - y100*YEAR100 - y004*YEAR004)/YEAR001;

yy = y400*4*100 + y100*100 + y004*4 + y001*1 + YEARFIRST;
dd = (ad - y400*YEAR400 - y100*YEAR100 - y004*YEAR004)%YEAR001;

    //月日
    if(0 == yy%1000)
    {
        if(0 == (yy/1000)%4)
        {
            m[1] = 29;
        }
    }
    else
    {
        if(0 == yy%4)
        {
            m[1] = 29;
        }
    }

    for(i = 1; i <= 12; i++)
    {
        if(dd - m[i] < 0)
        {
            break;
        }
        else
        {
            dd = dd -m[i];
        }
    }

    mm = i;
    //小时
    hh = sec/(60*60)%24;
    //分
    mi = sec/60 - sec/(60*60)*60;
    //秒
    ss = sec - sec/60*60;
    ms = usec;
    printf("%d-%02d-%02d %02d:%02d:%02d.%06d\n", yy, mm, dd, hh, mi, ss, ms);

return 1;
}