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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)gettimeofday.2 8.2 (Berkeley) 5/26/95 29.\" $FreeBSD: src/lib/libc/sys/gettimeofday.2,v 1.9.2.9 2003/02/11 06:05:00 nsayer Exp $ 30.\" $DragonFly: src/lib/libc/sys/gettimeofday.2,v 1.5 2008/05/02 02:05:04 swildner Exp $ 31.\" 32.Dd May 26, 1995 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 *tp" "struct timezone *tzp" 45.Ft int 46.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp" 47.Sh DESCRIPTION 48.Bf -symbolic 49Note: timezone is no longer used; this information is kept outside 50the kernel. 51.Ef 52.Pp 53The system's notion of the current Greenwich time and the current time 54zone is obtained with the 55.Fn gettimeofday 56call, and set with the 57.Fn settimeofday 58call. The time is expressed in seconds and microseconds 59since midnight (0 hour), January 1, 1970. The resolution of the system 60clock is hardware dependent, and the time may be updated continuously or 61in 62.Dq ticks . 63If 64.Fa tp 65or 66.Fa tzp 67is NULL, the associated time 68information will not be returned or set. 69.Pp 70The structures pointed to by 71.Fa tp 72and 73.Fa tzp 74are defined in 75.In sys/time.h 76as: 77.Bd -literal 78struct timeval { 79 long tv_sec; /* seconds since Jan. 1, 1970 */ 80 long tv_usec; /* and microseconds */ 81}; 82 83struct timezone { 84 int tz_minuteswest; /* minutes west of Greenwich */ 85 int tz_dsttime; /* type of dst correction */ 86}; 87.Ed 88.Pp 89The 90.Fa timezone 91structure indicates the local time zone 92(measured in minutes of time westward from Greenwich), 93and a flag that, if nonzero, indicates that 94Daylight Saving time applies locally during 95the appropriate part of the year. 96.Pp 97Only the super-user may set the time of day or time zone. 98If the system is running at securelevel \(>= 2 (see 99.Xr init 8 ) , 100the time may only be advanced or retarded by a maximum of one second. 101This limitation is imposed to prevent a malicious super-user 102from setting arbitrary time stamps on files. 103The system time can be adjusted backwards without restriction using the 104.Xr adjtime 2 105system call even when the system is secure. 106.Sh RETURN VALUES 107.Rv -std 108.Sh ERRORS 109The following error codes may be set in 110.Va errno : 111.Bl -tag -width Er 112.It Bq Er EFAULT 113An argument address referenced invalid memory. 114.It Bq Er EPERM 115A user other than the super-user attempted to set the time. 116.El 117.Sh SEE ALSO 118.Xr date 1 , 119.Xr adjtime 2 , 120.Xr ctime 3 , 121.Xr clocks 7 , 122.Xr timed 8 123.Sh HISTORY 124The 125.Fn gettimeofday 126function call appeared in 127.Bx 4.2 . 128