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.Dd May 13, 2021 29.Dt GETTIMEOFDAY 2 30.Os 31.Sh NAME 32.Nm gettimeofday , 33.Nm settimeofday 34.Nd get/set date and time 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In sys/time.h 39.Ft int 40.Fn gettimeofday "struct timeval *tp" "struct timezone *tzp" 41.Ft int 42.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp" 43.Sh DESCRIPTION 44The system's notion of the current Greenwich time and the current time 45zone is obtained with the 46.Fn gettimeofday 47system call, and set with the 48.Fn settimeofday 49system call. 50The time is expressed in seconds and microseconds 51since midnight (0 hour), January 1, 1970. 52The resolution of the system 53clock is hardware dependent, and the time may be updated continuously or 54in 55.Dq ticks . 56If 57.Fa tp 58or 59.Fa tzp 60is NULL, the associated time 61information will not be returned or set. 62.Pp 63The structures pointed to by 64.Fa tp 65and 66.Fa tzp 67are defined in 68.In sys/time.h 69as: 70.Bd -literal 71struct timeval { 72 time_t tv_sec; /* seconds */ 73 suseconds_t tv_usec; /* and microseconds */ 74}; 75 76struct timezone { 77 int tz_minuteswest; /* minutes west of Greenwich */ 78 int tz_dsttime; /* type of dst correction */ 79}; 80.Ed 81.Pp 82The 83.Vt timezone 84structure indicates the local time zone 85(measured in minutes of time westward from Greenwich), 86and a flag that, if nonzero, indicates that 87Daylight Saving time applies locally during 88the appropriate part of the year. 89The kernel generally does not track these values and they 90are usually returned as zero. 91Use 92.Xr localtime 3 93to find the offset for the currently active timezone. 94.Pp 95Only the super-user may set the time of day or time zone. 96If the system is running at securelevel >= 2 (see 97.Xr init 8 ) , 98the time may only be advanced or retarded by a maximum of one second. 99This limitation is imposed to prevent a malicious super-user 100from setting arbitrary time stamps on files. 101The system time can be adjusted backwards without restriction using the 102.Xr adjtime 2 103system call even when the system is secure. 104.Sh RETURN VALUES 105.Rv -std 106.Sh ERRORS 107The following error codes may be set in 108.Va errno : 109.Bl -tag -width Er 110.It Bq Er EINVAL 111The supplied 112.Fa timeval 113value is invalid. 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 clock_gettime 2 , 121.Xr ctime 3 , 122.Xr timeradd 3 , 123.Xr clocks 7 124.Sh HISTORY 125The 126.Fn gettimeofday 127system call appeared in 128.Bx 4.2 . 129