[apple/xnu.git] / bsd / man / man2 / gettimeofday.2

.\"	$OpenBSD: gettimeofday.2,v 1.5 1997/03/16 01:18:49 flipk Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)gettimeofday.2	8.2 (Berkeley) 5/26/95
.\"
.Dd May 26, 1995
.Dt GETTIMEOFDAY 2
.Os BSD 4
.Sh NAME
.Nm gettimeofday ,
.Nm settimeofday
.Nd get/set date and time
.Sh SYNOPSIS
.Fd #include <sys/time.h>
.Ft int
.Fn gettimeofday "struct timeval *tp" "struct timezone *tzp"
.Ft int
.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp"
.Sh DESCRIPTION
.Bf -symbolic
Note: timezone is no longer used; this information is kept outside
the kernel.
.Ef
.Pp
The system's notion of the current Greenwich time and the current time
zone is obtained with the
.Fn gettimeofday
call, and set with the
.Fn settimeofday
call.  The time is expressed in seconds and microseconds
since midnight (0 hour), January 1, 1970.  The resolution of the system
clock is hardware dependent, and the time may be updated continuously or
in ``ticks.''  If
.Fa tp
or
.Fa tzp
is NULL, the associated time
information will not be returned or set.
.Pp
The structures pointed to by
.Fa tp
and
.Fa tzp
are defined in 
.Ao Pa sys/time.h Ac
as:
.Pp
.Bd -literal
struct timeval {
	long	tv_sec;		/* seconds since Jan. 1, 1970 */
	long	tv_usec;	/* and microseconds */
};

struct timezone {
	int	tz_minuteswest; /* of Greenwich */
	int	tz_dsttime;	/* type of dst correction to apply */
};
.Ed
.Pp
The 
.Fa 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.
.Pp
Only the super-user may set the time of day or time zone.
If the system securelevel is greater than 1 (see
.Xr init 8 ),
the time may only be advanced.
This limitation is imposed to prevent a malicious super-user
from setting arbitrary time stamps on files.
The system time can still be adjusted backwards using the
.Xr adjtime 2
system call even when the system is secure.
.Sh RETURN
A 0 return value indicates that the call succeeded.
A -1 return value indicates an error occurred, and in this
case an error code is stored into the global variable
.Va errno .
.Sh ERRORS
The following error codes may be set in
.Va errno :
.Bl -tag -width [EFAULT]
.It Bq Er EFAULT
An argument address referenced invalid memory.
.It Bq Er EPERM
A user other than the super-user attempted to set the time.
.El
.Sh SEE ALSO
.Xr date 1 ,
.Xr adjtime 2 ,
.Xr ctime 3 ,
.Xr timed 8
.Sh HISTORY
The
.Fn gettimeofday
function call appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	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 .