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GETTIMEOFDAY(2)		    BSD	System Calls Manual	       GETTIMEOFDAY(2)

NAME
     gettimeofday, settimeofday	-- get/set date	and time

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <sys/time.h>

     int
     gettimeofday(struct timeval *tp, struct timezone *tzp);

     int
     settimeofday(const	struct timeval *tp, const struct timezone *tzp);

DESCRIPTION
     The system's notion of the	current	Greenwich time and the current time
     zone is obtained with the gettimeofday() system call, and set with	the
     settimeofday() system call.  The time is expressed	in seconds and mi-
     croseconds	since midnight (0 hour), January 1, 1970.  The resolution of
     the system	clock is hardware dependent, and the time may be updated con-
     tinuously or in "ticks".  If tp or	tzp is NULL, the associated time in-
     formation will not	be returned or set.

     The structures pointed to by tp and tzp are defined in <sys/time.h> as:

     struct timeval {
	     time_t	     tv_sec;	     /*	seconds	*/
	     suseconds_t     tv_usec;	     /*	and microseconds */
     };

     struct timezone {
	     int     tz_minuteswest; /*	minutes	west of	Greenwich */
	     int     tz_dsttime;     /*	type of	dst correction */
     };

     The timezone structure indicates the local	time zone (measured in minutes
     of	time westward from Greenwich), and a flag that,	if nonzero, indicates
     that Daylight Saving time applies locally during the appropriate part of
     the year.

     Only the super-user may set the time of day or time zone.	If the system
     is	running	at securelevel >= 2 (see init(8)), the time may	only be	ad-
     vanced or retarded	by a maximum of	one second.  This limitation is	im-
     posed to prevent a	malicious super-user from setting arbitrary time
     stamps on files.  The system time can be adjusted backwards without re-
     striction using the adjtime(2) system call	even when the system is	se-
     cure.

RETURN VALUES
     Upon successful completion, the value 0 is	returned; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The following error codes may be set in errno:

     [EINVAL]		The supplied timeval value is invalid.

     [EPERM]		A user other than the super-user attempted to set the
			time.

SEE ALSO
     date(1), adjtime(2), clock_gettime(2), ctime(3), timeradd(3), clocks(7),
     timed(8)

HISTORY
     The gettimeofday()	system call appeared in	4.2BSD.

BSD				August 4, 2018				   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY

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