1.\" $NetBSD: gettimeofday.2,v 1.18 2002/02/08 01:28:18 ross 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 39.Sh NAME 40.Nm gettimeofday , 41.Nm settimeofday 42.Nd get/set date and time 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.Fd #include \*[Lt]sys/time.h\*[Gt] 47.Ft int 48.Fn gettimeofday "struct timeval *tp" "struct timezone *tzp" 49.Ft int 50.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp" 51.Sh DESCRIPTION 52.Bf -symbolic 53Note: time zone information is no longer provided by this interface. 54See 55.Xr localtime 3 56for information on how to retrieve it. 57.Ef 58.Pp 59The system's notion of the current UTC time is obtained with the 60.Fn gettimeofday 61call, and set with the 62.Fn settimeofday 63call. The time is expressed in seconds and microseconds 64since midnight (0 hour), January 1, 1970. The resolution of the system 65clock is hardware dependent, and the time may be updated continuously or 66in ``ticks.'' If 67.Fa tp 68is NULL, the time will not be returned or set. 69.Pp 70The structures pointed to by 71.Fa tp 72and 73.Fa tzp 74are defined in 75.Ao Pa sys/time.h Ac 76as: 77.Pp 78.Bd -literal 79struct timeval { 80 long tv_sec; /* seconds since Jan. 1, 1970 */ 81 long tv_usec; /* and microseconds */ 82}; 83 84struct timezone { 85 int tz_minuteswest; /* of Greenwich */ 86 int tz_dsttime; /* type of dst correction to apply */ 87}; 88.Ed 89.Pp 90The 91.Fa timezone 92structure is provided only for source compatibility. It is ignored by 93.Fn settimeofday , 94and 95.Fn gettimeofday 96will always return zeroes. 97.Pp 98If the calling user is not the super-user, then the 99.Fn settimeofday 100function in the standard C library will try to use the 101.Xr clockctl 4 102device if present, thus making possible for non privileged users to 103set the system time. If 104.Xr clockctl 4 105is not present or not accessible, then 106.Fn settimeofday 107reverts to the 108.Fn settimeofday 109system call, which is restricted to the super user. 110.\" XXX uncomment when/if this is put into place! 111.\" If the system is running in secure mode (see 112.\" .Xr init 8 ), 113.\" the time may only be advanced. 114.\" This limitation is imposed to prevent a malicious super user 115.\" from setting arbitrary time stamps on files. 116.\" The system time can still be adjusted backwards using the 117.\" .Xr adjtime 2 118.\" system call even when the system is secure. 119.Sh RETURN VALUES 120A 0 return value indicates that the call succeeded. 121A -1 return value indicates an error occurred, and in this 122case an error code is stored into the global variable 123.Va errno . 124.Sh ERRORS 125The following error codes may be set in 126.Va errno : 127.Bl -tag -width Er 128.It Bq Er EFAULT 129An argument address referenced invalid memory. 130.It Bq Er EPERM 131A user other than the super user attempted to set the time, or the specified 132time was less than the current time, which was not permitted at the current 133security level. 134.El 135.Sh SEE ALSO 136.Xr date 1 , 137.Xr adjtime 2 , 138.Xr ctime 3 , 139.Xr localtime 3 , 140.Xr clockctl 4 , 141.Xr timed 8 142.Sh HISTORY 143The 144.Fn gettimeofday 145function call appeared in 146.Bx 4.2 . 147The 148.Fa tzp 149argument was deprecated in 150.Bx 4.4 151(and many other systems). 152