linux打印一个精确到毫秒级的时间

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

int main(int argc ,char *argv[])
{

char buf[25] = {0};
struct timeval tv;
struct tm      tm;
size_t         len = 28;

memset(tv, 0, sizeof(tv));
memset(tm, 0, sizeof(tm));
gettimeofday(&tv, NULL);
localtime_r(&tv.tv_sec, &tm);
strftime(buf, len, "%Y-%m-%d %H:%M:%S", &tm);
len = strlen(buf);
sprintf(buf + len, ".%-6.3d", (int)(tv.tv_usec/1000));
printf("%s\n", buf);

return 0;
}