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.\" 4. 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 May 26, 1995 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 47.Bf -symbolic 48Note: timezone is no longer used; this information is kept outside 49the kernel. 50.Ef 51.Pp 52The system's notion of the current Greenwich time and the current time 53zone is obtained with the 54.Fn gettimeofday 55system call, and set with the 56.Fn settimeofday 57system call. 58The time is expressed in seconds and microseconds 59since midnight (0 hour), January 1, 1970. 60The resolution of the system 61clock is hardware dependent, and the time may be updated continuously or 62in 63.Dq ticks . 64If 65.Fa tp 66or 67.Fa tzp 68is NULL, the associated time 69information will not be returned or set. 70.Pp 71The structures pointed to by 72.Fa tp 73and 74.Fa tzp 75are defined in 76.In sys/time.h 77as: 78.Bd -literal 79struct timeval { 80 time_t tv_sec; /* seconds */ 81 suseconds_t tv_usec; /* and microseconds */ 82}; 83 84struct timezone { 85 int tz_minuteswest; /* minutes west of Greenwich */ 86 int tz_dsttime; /* type of dst correction */ 87}; 88.Ed 89.Pp 90The 91.Vt timezone 92structure indicates the local time zone 93(measured in minutes of time westward from Greenwich), 94and a flag that, if nonzero, indicates that 95Daylight Saving time applies locally during 96the appropriate part of the year. 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 EFAULT 114An argument address referenced invalid memory. 115.It Bq Er EPERM 116A user other than the super-user attempted to set the time. 117.El 118.Sh SEE ALSO 119.Xr date 1 , 120.Xr adjtime 2 , 121.Xr clock_gettime 2 , 122.Xr ctime 3 , 123.Xr timeradd 3 , 124.Xr clocks 7 , 125.Xr timed 8 126.Sh HISTORY 127The 128.Fn gettimeofday 129system call appeared in 130.Bx 4.2 . 131