1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)gettimeofday.2 8.2 (Berkeley) 5/26/95 33.\" $FreeBSD: src/lib/libc/sys/gettimeofday.2,v 1.9.2.9 2003/02/11 06:05:00 nsayer Exp $ 34.\" $DragonFly: src/lib/libc/sys/gettimeofday.2,v 1.5 2008/05/02 02:05:04 swildner Exp $ 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.In sys/time.h 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: timezone is no longer used; this information is kept outside 54the kernel. 55.Ef 56.Pp 57The system's notion of the current Greenwich time and the current time 58zone is obtained with the 59.Fn gettimeofday 60call, and set with the 61.Fn settimeofday 62call. The time is expressed in seconds and microseconds 63since midnight (0 hour), January 1, 1970. The resolution of the system 64clock is hardware dependent, and the time may be updated continuously or 65in 66.Dq ticks . 67If 68.Fa tp 69or 70.Fa tzp 71is NULL, the associated time 72information will not be returned or set. 73.Pp 74The structures pointed to by 75.Fa tp 76and 77.Fa tzp 78are defined in 79.In sys/time.h 80as: 81.Bd -literal 82struct timeval { 83 long tv_sec; /* seconds since Jan. 1, 1970 */ 84 long tv_usec; /* and microseconds */ 85}; 86 87struct timezone { 88 int tz_minuteswest; /* minutes west of Greenwich */ 89 int tz_dsttime; /* type of dst correction */ 90}; 91.Ed 92.Pp 93The 94.Fa timezone 95structure indicates the local time zone 96(measured in minutes of time westward from Greenwich), 97and a flag that, if nonzero, indicates that 98Daylight Saving time applies locally during 99the appropriate part of the year. 100.Pp 101Only the super-user may set the time of day or time zone. 102If the system is running at securelevel \(>= 2 (see 103.Xr init 8 ) , 104the time may only be advanced or retarded by a maximum of one second. 105This limitation is imposed to prevent a malicious super-user 106from setting arbitrary time stamps on files. 107The system time can be adjusted backwards without restriction using the 108.Xr adjtime 2 109system call even when the system is secure. 110.Sh RETURN VALUES 111.Rv -std 112.Sh ERRORS 113The following error codes may be set in 114.Va errno : 115.Bl -tag -width Er 116.It Bq Er EFAULT 117An argument address referenced invalid memory. 118.It Bq Er EPERM 119A 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 clocks 7 , 126.Xr timed 8 127.Sh HISTORY 128The 129.Fn gettimeofday 130function call appeared in 131.Bx 4.2 . 132