Second, Millisecond(毫秒), Microsecond(微秒)

gettimeofday()
struct timeval {
  // seconds since Jan. 1, 1970
  time_t       tv_sec;  
  //  and microseconds
  suseconds_t  tv_usec;   
};
     
     

#include "stdio.h"
#include "sys/time.h"
// for sleep
#include "unistd.h"

void showtime(){
  struct timeval tv;
  gettimeofday(&tv,NULL);
  printf("second     :%ld\n",tv.tv_sec);
  printf("millisecond:%ld\n",tv.tv_sec*1000 + tv.tv_usec/1000);
  printf("microsecond:%ld\n",tv.tv_sec*1000000 + tv.tv_usec);  
}

int main(){
    showtime();
    printf("\n");
    sleep(1);
    showtime();
    return 0;
}


second     :1631610949
millisecond:1631610949920
microsecond:1631610949920783

second     :1631610950
millisecond:1631610950921
microsecond:1631610950921375