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 April 28, 2024 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 46.Em Note : 47The 48.Nm gettimeofday 49function 50.Po but not 51.Nm settimeofday Pc 52is obsolescent. 53See the 54.Sx STANDARDS 55section for more details. 56.Pp 57The system's notion of the current Greenwich time and the current time 58zone is obtained with the 59.Fn gettimeofday 60system call, and set with the 61.Fn settimeofday 62system call. 63The time is expressed in seconds and microseconds 64since midnight (0 hour), January 1, 1970. 65The resolution of the system 66clock is hardware dependent, and the time may be updated continuously or 67in 68.Dq ticks . 69If 70.Fa tp 71or 72.Fa tzp 73is NULL, the associated time 74information will not be returned or set. 75.Pp 76The structures pointed to by 77.Fa tp 78and 79.Fa tzp 80are defined in 81.In sys/time.h 82as: 83.Bd -literal 84struct timeval { 85 time_t tv_sec; /* seconds */ 86 suseconds_t tv_usec; /* and microseconds */ 87}; 88 89struct timezone { 90 int tz_minuteswest; /* minutes west of Greenwich */ 91 int tz_dsttime; /* type of dst correction */ 92}; 93.Ed 94.Pp 95The 96.Vt timezone 97structure indicates the local time zone 98(measured in minutes of time westward from Greenwich), 99and a flag that, if nonzero, indicates that 100Daylight Saving time applies locally during 101the appropriate part of the year. 102The kernel generally does not track these values and they 103are usually returned as zero. 104Use 105.Xr localtime 3 106to find the offset for the currently active timezone. 107.Pp 108Only the super-user may set the time of day or time zone. 109If the system is running at securelevel >= 2 (see 110.Xr init 8 ) , 111the time may only be advanced or retarded by a maximum of one second. 112This limitation is imposed to prevent a malicious super-user 113from setting arbitrary time stamps on files. 114The system time can be adjusted backwards without restriction using the 115.Xr adjtime 2 116system call even when the system is secure. 117.Sh RETURN VALUES 118.Rv -std 119.Sh ERRORS 120The following error codes may be set in 121.Va errno : 122.Bl -tag -width Er 123.It Bq Er EINVAL 124The supplied 125.Fa timeval 126value is invalid. 127.It Bq Er EPERM 128A user other than the super-user attempted to set the time. 129.El 130.Sh SEE ALSO 131.Xr date 1 , 132.Xr adjtime 2 , 133.Xr clock_gettime 2 , 134.Xr ctime 3 , 135.Xr timeradd 3 , 136.Xr clocks 7 137.Sh STANDARDS 138The 139.Nm gettimeofday 140function is considered obsolescent and its usage discouraged by 141.\" XXX: This should be replaced in the future when an appropriate argument to 142.\" the St macro is available: -p1003.1-2017 143.No IEEE Std 1003.1-2008, 2017 Edition (\\(LqPOSIX.1\\(Rq) . 144Applications should use the 145.Xr clock_gettime 2 146function instead. 147.Sh HISTORY 148The 149.Fn gettimeofday 150system call appeared in 151.Bx 4.2 . 152