1.\" $NetBSD: time_second.9,v 1.9 2020/04/18 18:55:20 wiz Exp $ 2.\" 3.\" Copyright (c) 1994 Christopher G. Demetriou 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed for the 17.\" NetBSD Project. See http://www.NetBSD.org/ for 18.\" information about NetBSD. 19.\" 4. The name of the author may not be used to endorse or promote products 20.\" derived from this software without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32.\" 33.\" <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>> 34.\" 35.Dd April 17, 2020 36.Dt TIME_SECOND 9 37.Os 38.Sh NAME 39.Nm time_second , 40.Nm time_uptime 41.Nd system time variables 42.Sh SYNOPSIS 43.In sys/time.h 44.Vt extern time_t time_second; 45.Vt extern time_t time_uptime; 46.Sh DESCRIPTION 47The 48.Va time_second 49variable is the system's 50.Dq wall time 51clock. 52It is set at boot by 53.Xr inittodr 9 , 54and is updated periodically via 55.Xr timecounter 9 56framework, and also updated by the 57.Xr settimeofday 2 58system call. 59.Pp 60The 61.Va time_uptime 62variable is a monotonically increasing system clock. 63It is set at boot, and is updated periodically. 64(It is not updated by 65.Xr settimeofday 2 . ) 66.Pp 67All of these variables contain times 68expressed in seconds since midnight (0 hour), 69January 1, 1970, UTC. 70.Pp 71The 72.Xr bintime 9 , 73.Xr getbintime 9 , 74.Xr microtime 9 , 75.Xr getmicrotime 9 , 76.Xr nanotime 9 , 77and 78.Xr getnanotime 9 79functions can be used to get the current time more accurately and in an 80atomic manner. 81.Pp 82Similarly, the 83.Xr binuptime 9 , 84.Xr getbinuptime 9 , 85.Xr microuptime 9 , 86.Xr getmicrouptime 9 , 87.Xr nanouptime 9 , 88and 89.Xr getnanouptime 9 90functions can be used to get the time elapsed since boot more accurately 91and in an atomic manner. 92.Sh SEE ALSO 93.Xr clock_settime 2 , 94.Xr ntp_adjtime 2 , 95.Xr timespec 3 , 96.Xr hardclock 9 , 97.Xr hz 9 98