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.\" 30.Dd May 13, 2021 31.Dt GETTIMEOFDAY 2 32.Os 33.Sh NAME 34.Nm gettimeofday , 35.Nm settimeofday 36.Nd get/set date and time 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In sys/time.h 41.Ft int 42.Fn gettimeofday "struct timeval *tp" "struct timezone *tzp" 43.Ft int 44.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp" 45.Sh DESCRIPTION 46The system's notion of the current Greenwich time and the current time 47zone is obtained with the 48.Fn gettimeofday 49system call, and set with the 50.Fn settimeofday 51system call. 52The time is expressed in seconds and microseconds 53since midnight (0 hour), January 1, 1970. 54The resolution of the system 55clock is hardware dependent, and the time may be updated continuously or 56in 57.Dq ticks . 58If 59.Fa tp 60or 61.Fa tzp 62is NULL, the associated time 63information will not be returned or set. 64.Pp 65The structures pointed to by 66.Fa tp 67and 68.Fa tzp 69are defined in 70.In sys/time.h 71as: 72.Bd -literal 73struct timeval { 74 time_t tv_sec; /* seconds */ 75 suseconds_t tv_usec; /* and microseconds */ 76}; 77 78struct timezone { 79 int tz_minuteswest; /* minutes west of Greenwich */ 80 int tz_dsttime; /* type of dst correction */ 81}; 82.Ed 83.Pp 84The 85.Vt timezone 86structure indicates the local time zone 87(measured in minutes of time westward from Greenwich), 88and a flag that, if nonzero, indicates that 89Daylight Saving time applies locally during 90the appropriate part of the year. 91The kernel generally does not track these values and they 92are usually returned as zero. 93Use 94.Xr localtime 3 95to find the offset for the currently active timezone. 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 EINVAL 113The supplied 114.Fa timeval 115value is invalid. 116.It Bq Er EPERM 117A user other than the super-user attempted to set the time. 118.El 119.Sh SEE ALSO 120.Xr date 1 , 121.Xr adjtime 2 , 122.Xr clock_gettime 2 , 123.Xr ctime 3 , 124.Xr timeradd 3 , 125.Xr clocks 7 126.Sh HISTORY 127The 128.Fn gettimeofday 129system call appeared in 130.Bx 4.2 . 131