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.\" $FreeBSD$ 30.\" 31.Dd October 27, 2018 32.Dt GETTIMEOFDAY 2 33.Os 34.Sh NAME 35.Nm gettimeofday , 36.Nm settimeofday 37.Nd get/set date and time 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/time.h 42.Ft int 43.Fn gettimeofday "struct timeval *tp" "struct timezone *tzp" 44.Ft int 45.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp" 46.Sh DESCRIPTION 47The system's notion of the current Greenwich time and the current time 48zone is obtained with the 49.Fn gettimeofday 50system call, and set with the 51.Fn settimeofday 52system call. 53The time is expressed in seconds and microseconds 54since midnight (0 hour), January 1, 1970. 55The resolution of the system 56clock is hardware dependent, and the time may be updated continuously or 57in 58.Dq ticks . 59If 60.Fa tp 61or 62.Fa tzp 63is NULL, the associated time 64information will not be returned or set. 65.Pp 66The structures pointed to by 67.Fa tp 68and 69.Fa tzp 70are defined in 71.In sys/time.h 72as: 73.Bd -literal 74struct timeval { 75 time_t tv_sec; /* seconds */ 76 suseconds_t tv_usec; /* and microseconds */ 77}; 78 79struct timezone { 80 int tz_minuteswest; /* minutes west of Greenwich */ 81 int tz_dsttime; /* type of dst correction */ 82}; 83.Ed 84.Pp 85The 86.Vt timezone 87structure indicates the local time zone 88(measured in minutes of time westward from Greenwich), 89and a flag that, if nonzero, indicates that 90Daylight Saving time applies locally during 91the appropriate part of the year. 92The kernel generally does not track these values and they 93are usually returned as zero. 94Use 95.Xr localtime 3 96to find the offset for the currently active timezone. 97.Pp 98Only the super-user may set the time of day or time zone. 99If the system is running at securelevel >= 2 (see 100.Xr init 8 ) , 101the time may only be advanced or retarded by a maximum of one second. 102This limitation is imposed to prevent a malicious super-user 103from setting arbitrary time stamps on files. 104The system time can be adjusted backwards without restriction using the 105.Xr adjtime 2 106system call even when the system is secure. 107.Sh RETURN VALUES 108.Rv -std 109.Sh ERRORS 110The following error codes may be set in 111.Va errno : 112.Bl -tag -width Er 113.It Bq Er EINVAL 114The supplied 115.Fa timeval 116value is invalid. 117.It Bq Er EPERM 118A user other than the super-user attempted to set the time. 119.El 120.Sh SEE ALSO 121.Xr date 1 , 122.Xr adjtime 2 , 123.Xr clock_gettime 2 , 124.Xr ctime 3 , 125.Xr timeradd 3 , 126.Xr clocks 7 , 127.Xr timed 8 128.Sh HISTORY 129The 130.Fn gettimeofday 131system call appeared in 132.Bx 4.2 . 133