12. Gettimeofday() and time()

1. gettimeofday()
   gettimeofday() Can be found in tv The buffer pointed to is returned from Epoch（UTC 1970.1.1 00:00:00） Seconds since , Date stored in time_t Variable of type , This is a SUSv3 Defined integer type ）

#include <sys/time.h>

int gettimeofday(struct timeval *tv, struct timezone*tz);
	Returns 0 on success, or -1 on error

Parameters tv Is a pointer to the following data structure :

struct timeval{
    
	time_t	tv_sec;	/*Seconds since 00:00:00, 1 Jan 1970 UTC*/
	suseconds_t tv_sec;	/*Addtional microseconds (long int)*/
}

Parameters tz Has been abandoned , Pass in on use NULL that will do .
2.time()
time() The function also returns from Epoch Seconds since , This is due to historical reasons ,gettimeofday() More accurate , later time() It is right gettimeofday() Call to .

#include <time.h>
time_t time(time_t *timep);
	Returns number of seconds since the Epoch or (time_t)-1 on error

time() Return the number of seconds in two ways , Parameters timep Or return value , But to avoid mistakes , Usually simply call ：

time_t t = time(NULL);

Reference material ：《Linuc/UNIX System programming manual 》