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 April 28, 2024 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 44.Em Note : 45The 46.Nm gettimeofday 47function 48.Po but not 49.Nm settimeofday Pc 50is obsolescent. 51See the 52.Sx STANDARDS 53section for more details. 54.Pp 55The system's notion of the current Greenwich time and the current time 56zone is obtained with the 57.Fn gettimeofday 58system call, and set with the 59.Fn settimeofday 60system call. 61The time is expressed in seconds and microseconds 62since midnight (0 hour), January 1, 1970. 63The 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 time_t tv_sec; /* seconds */ 84 suseconds_t 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.Vt 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. 100The kernel generally does not track these values and they 101are usually returned as zero. 102Use 103.Xr localtime 3 104to find the offset for the currently active timezone. 105.Pp 106Only the super-user may set the time of day or time zone. 107If the system is running at securelevel >= 2 (see 108.Xr init 8 ) , 109the time may only be advanced or retarded by a maximum of one second. 110This limitation is imposed to prevent a malicious super-user 111from setting arbitrary time stamps on files. 112The system time can be adjusted backwards without restriction using the 113.Xr adjtime 2 114system call even when the system is secure. 115.Sh RETURN VALUES 116.Rv -std 117.Sh ERRORS 118The following error codes may be set in 119.Va errno : 120.Bl -tag -width Er 121.It Bq Er EINVAL 122The supplied 123.Fa timeval 124value is invalid. 125.It Bq Er EPERM 126A user other than the super-user attempted to set the time. 127.El 128.Sh SEE ALSO 129.Xr date 1 , 130.Xr adjtime 2 , 131.Xr clock_gettime 2 , 132.Xr ctime 3 , 133.Xr timeradd 3 , 134.Xr clocks 7 135.Sh STANDARDS 136The 137.Nm gettimeofday 138function is considered obsolescent and its usage discouraged by 139.\" XXX: This should be replaced in the future when an appropriate argument to 140.\" the St macro is available: -p1003.1-2017 141.No IEEE Std 1003.1-2008, 2017 Edition (\\(LqPOSIX.1\\(Rq) . 142Applications should use the 143.Xr clock_gettime 2 144function instead. 145.Sh HISTORY 146The 147.Fn gettimeofday 148system call appeared in 149.Bx 4.2 . 150