1.\" $NetBSD: gettimeofday.2,v 1.25 2006/10/13 20:57:32 wiz 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)gettimeofday.2 8.2 (Berkeley) 5/26/95 31.\" 32.Dd April 26, 2004 33.Dt GETTIMEOFDAY 2 34.Os 35.Sh NAME 36.Nm gettimeofday , 37.Nm settimeofday 38.Nd get/set date and time 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/time.h 43.Ft int 44.Fn gettimeofday "struct timeval * restrict tp" "void * restrict tzp" 45.Ft int 46.Fn settimeofday "const struct timeval * restrict tp" "const void * restrict tzp" 47.Sh DESCRIPTION 48.Bf -symbolic 49Note: time zone information is no longer provided by this interface. 50See 51.Xr localtime 3 52for information on how to retrieve it. 53.Ef 54.Pp 55The system's notion of the current UTC time is obtained with the 56.Fn gettimeofday 57call, and set with the 58.Fn settimeofday 59call. 60The time is expressed in seconds and microseconds 61since midnight (0 hour), January 1, 1970. 62The resolution of the system clock is hardware dependent, 63and the time may be updated continuously or in ``ticks.'' 64If 65.Fa tp 66is NULL, the time will not be returned or set. 67Despite being declared 68.Fa void * , 69the objects pointed to by 70.Fa tzp 71shall be of type 72.Fa struct timezone . 73.Pp 74The structures pointed to by 75.Fa tp 76and 77.Fa tzp 78are defined in 79.Ao Pa sys/time.h Ac 80as: 81.Pp 82.Bd -literal 83struct timeval { 84 long tv_sec; /* seconds since Jan. 1, 1970 */ 85 long tv_usec; /* and microseconds */ 86}; 87 88struct timezone { 89 int tz_minuteswest; /* of Greenwich */ 90 int tz_dsttime; /* type of dst correction to apply */ 91}; 92.Ed 93.Pp 94The 95.Fa timezone 96structure is provided only for source compatibility. 97It is ignored by 98.Fn settimeofday , 99and 100.Fn gettimeofday 101will always return zeroes. 102.Pp 103If the calling user is not the super-user, then the 104.Fn settimeofday 105function in the standard C library will try to use the 106.Xr clockctl 4 107device if present, thus making possible for non privileged users to 108set the system time. 109If 110.Xr clockctl 4 111is not present or not accessible, then 112.Fn settimeofday 113reverts to the 114.Fn settimeofday 115system call, which is restricted to the super user. 116.\" XXX uncomment when/if this is put into place! 117.\" If the system is running in secure mode (see 118.\" .Xr init 8 ), 119.\" the time may only be advanced. 120.\" This limitation is imposed to prevent a malicious super user 121.\" from setting arbitrary time stamps on files. 122.\" The system time can still be adjusted backwards using the 123.\" .Xr adjtime 2 124.\" system call even when the system is secure. 125.Sh RETURN VALUES 126A 0 return value indicates that the call succeeded. 127A \-1 return value indicates an error occurred, and in this 128case an error code is stored into the global variable 129.Va errno . 130.Sh ERRORS 131The following error codes may be set in 132.Va errno : 133.Bl -tag -width Er 134.It Bq Er EFAULT 135An argument address referenced invalid memory. 136.It Bq Er EPERM 137A user other than the super user attempted to set the time, or the specified 138time was less than the current time, which was not permitted at the current 139security level. 140.El 141.Sh SEE ALSO 142.Xr date 1 , 143.Xr adjtime 2 , 144.Xr ctime 3 , 145.Xr localtime 3 , 146.Xr clockctl 4 , 147.Xr timed 8 148.Sh HISTORY 149The 150.Fn gettimeofday 151function call appeared in 152.Bx 4.2 . 153The 154.Fa tzp 155argument was deprecated in 156.Bx 4.4 157(and many other systems). 158