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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	.Fo gettimeofday
	47	.Fa "struct timeval *restrict tp"
	48	.Fa "void *restrict tzp"
	49	.Fc
	50	.Ft int
	51	.Fo settimeofday
	52	.Fa "const struct timeval *tp"
	53	.Fa "const struct timezone *tzp"
	54	.Fc
	55	.Sh DESCRIPTION
	56	.Bf -symbolic
	57	Note: timezone is no longer used; this information is kept outside
	58	the kernel.
	59	.Ef
	60	.Pp
	61	The system's notion of the current Greenwich time and the current time
	62	zone is obtained with the
	63	.Fn gettimeofday
	64	call, and set with the
	65	.Fn settimeofday
	66	call. The time is expressed in seconds and microseconds
	67	since midnight (0 hour), January 1, 1970. The resolution of the system
	68	clock is hardware dependent, and the time may be updated continuously or
	69	in ``ticks.'' If
	70	.Fa tp
	71	or
	72	.Fa tzp
	73	is NULL, the associated time
	74	information will not be returned or set.
	75	.Pp
	76	The structures pointed to by
	77	.Fa tp
	78	and
	79	.Fa tzp
	80	are defined in
	81	.Ao Pa sys/time.h Ac
	82	as:
	83	.Pp
	84	.Bd -literal
	85	struct timeval {
	86	time_t tv_sec; /* seconds since Jan. 1, 1970 */
	87	suseconds_t tv_usec; /* and microseconds */
	88	};
	89
	90	struct timezone {
	91	int tz_minuteswest; /* of Greenwich */
	92	int tz_dsttime; /* type of dst correction to apply */
	93	};
	94	.Ed
	95	.Pp
	96	The
	97	.Fa timeval
	98	structure specifies a time value in seconds and microseconds.
	99	The values in
	100	.Fa timeval
	101	are opaque types whose length may vary on different machines;
	102	depending on them to have any given length may lead to errors.
	103	.Pp
	104	The
	105	.Fa timezone
	106	structure indicates the local time zone
	107	(measured in minutes of time westward from Greenwich),
	108	and a flag that, if nonzero, indicates that
	109	Daylight Saving time applies locally during
	110	the appropriate part of the year.
	111	.Pp
	112	Only the super-user may set the time of day or time zone.
	113	If the system securelevel is greater than 1 (see
	114	.Xr init 8 ),
	115	the time may only be advanced.
	116	This limitation is imposed to prevent a malicious super-user
	117	from setting arbitrary time stamps on files.
	118	The system time can still be adjusted backwards using the
	119	.Xr adjtime 2
	120	system call even when the system is secure.
	121	.Sh RETURN
	122	A 0 return value indicates that the call succeeded.
	123	A -1 return value indicates an error occurred, and in this
	124	case an error code is stored into the global variable
	125	.Va errno .
	126	.Sh ERRORS
	127	The following error codes may be set in
	128	.Va errno :
	129	.Bl -tag -width [EFAULT]
	130	.It Bq Er EFAULT
	131	An argument address referenced invalid memory.
	132	.It Bq Er EPERM
	133	A user other than the super-user attempted to set the time.
	134	.El
	135	.Sh LEGACY SYNOPSIS
	136	.Fd #include <sys/time.h>
	137	.Pp
	138	.Ft int
	139	.br
	140	.Fo gettimeofday
	141	.Fa "struct timeval *tp"
	142	.Fa "struct timezone *tzp"
	143	.Fc ;
	144	.Pp
	145	The type of
	146	.Fa tzp
	147	has changed.
	148	.Sh SEE ALSO
	149	.Xr date 1 ,
	150	.Xr adjtime 2 ,
	151	.Xr ctime 3 ,
	152	.Xr compat 5 ,
	153	.Xr timed 8
	154	.Sh HISTORY
	155	The
	156	.Fn gettimeofday
	157	function call appeared in
	158	.Bx 4.2 .