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	1	.\" $OpenBSD: gettimeofday.2,v 1.5 1997/03/16 01:18:49 flipk Exp $
	2	.\"
	3	.\" Copyright (c) 1980, 1991, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)gettimeofday.2 8.2 (Berkeley) 5/26/95
	35	.\"
	36	.Dd May 26, 1995
	37	.Dt GETTIMEOFDAY 2
	38	.Os BSD 4
	39	.Sh NAME
	40	.Nm gettimeofday ,
	41	.Nm settimeofday
	42	.Nd get/set date and time
	43	.Sh SYNOPSIS
	44	.Fd #include <sys/time.h>
	45	.Ft int
	46	.Fn gettimeofday "struct timeval tp" "struct timezone tzp"
	47	.Ft int
	48	.Fn settimeofday "const struct timeval tp" "const struct timezone tzp"
	49	.Sh DESCRIPTION
	50	.Bf -symbolic
	51	Note: timezone is no longer used; this information is kept outside
	52	the kernel.
	53	.Ef
	54	.Pp
	55	The system's notion of the current Greenwich time and the current time
	56	zone is obtained with the
	57	.Fn gettimeofday
	58	call, and set with the
	59	.Fn settimeofday
	60	call. The time is expressed in seconds and microseconds
	61	since midnight (0 hour), January 1, 1970. The resolution of the system
	62	clock is hardware dependent, and the time may be updated continuously or
	63	in ``ticks.'' If
	64	.Fa tp
	65	or
	66	.Fa tzp
	67	is NULL, the associated time
	68	information will not be returned or set.
	69	.Pp
	70	The structures pointed to by
	71	.Fa tp
	72	and
	73	.Fa tzp
	74	are defined in
	75	.Ao Pa sys/time.h Ac
	76	as:
	77	.Pp
	78	.Bd -literal
	79	struct timeval {
	80	long tv_sec; /* seconds since Jan. 1, 1970 */
	81	long tv_usec; /* and microseconds */
	82	};
	83
	84	struct timezone {
	85	int tz_minuteswest; /* of Greenwich */
	86	int tz_dsttime; /* type of dst correction to apply */
	87	};
	88	.Ed
	89	.Pp
	90	The
	91	.Fa timezone
	92	structure indicates the local time zone
	93	(measured in minutes of time westward from Greenwich),
	94	and a flag that, if nonzero, indicates that
	95	Daylight Saving time applies locally during
	96	the appropriate part of the year.
	97	.Pp
	98	Only the super-user may set the time of day or time zone.
	99	If the system securelevel is greater than 1 (see
	100	.Xr init 8 ),
	101	the time may only be advanced.
	102	This limitation is imposed to prevent a malicious super-user
	103	from setting arbitrary time stamps on files.
	104	The system time can still be adjusted backwards using the
	105	.Xr adjtime 2
	106	system call even when the system is secure.
	107	.Sh RETURN
	108	A 0 return value indicates that the call succeeded.
	109	A -1 return value indicates an error occurred, and in this
	110	case an error code is stored into the global variable
	111	.Va errno .
	112	.Sh ERRORS
	113	The following error codes may be set in
	114	.Va errno :
	115	.Bl -tag -width [EFAULT]
	116	.It Bq Er EFAULT
	117	An argument address referenced invalid memory.
	118	.It Bq Er EPERM
	119	A user other than the super-user attempted to set the time.
	120	.El
	121	.Sh SEE ALSO
	122	.Xr date 1 ,
	123	.Xr adjtime 2 ,
	124	.Xr ctime 3 ,
	125	.Xr timed 8
	126	.Sh HISTORY
	127	The
	128	.Fn gettimeofday
	129	function call appeared in
	130	.Bx 4.2 .