1.\" $NetBSD: time.9,v 1.1 1995/11/25 21:24:53 perry 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 by Christopher G. Demetriou 17.\" for the NetBSD Project. 18.\" 3. The name of the author may not be used to endorse or promote products 19.\" derived from this software without specific prior written permission 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 22.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 23.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 24.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 25.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 26.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 30.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31.\" 32.\" $FreeBSD$ 33.\" 34.Dd September 17, 2004 35.Dt TIME 9 36.Os 37.Sh NAME 38.Nm boottime , 39.Nm time_second , 40.Nm time_uptime 41.Nd system time variables 42.Sh SYNOPSIS 43.In sys/time.h 44.Pp 45.Vt extern struct timeval boottime ; 46.Vt extern time_t time_second ; 47.Vt extern time_t time_uptime ; 48.Sh DESCRIPTION 49The 50.Va boottime 51variable holds the system boot time. 52.Pp 53The 54.Va time_second 55variable is the system's 56.Dq wall time 57clock to the second. 58.Pp 59The 60.Va time_uptime 61variable is the number of seconds since boot. 62.Pp 63The 64.Xr bintime 9 , 65.Xr getbintime 9 , 66.Xr microtime 9 , 67.Xr getmicrotime 9 , 68.Xr nanotime 9 , 69and 70.Xr getnanotime 9 71functions can be used to get the current time more accurately and in an 72atomic manner. 73Similarly, the 74.Xr binuptime 9 , 75.Xr getbinuptime 9 , 76.Xr microuptime 9 , 77.Xr getmicrouptime 9 , 78.Xr nanouptime 9 , 79and 80.Xr getnanouptime 9 81functions can be used to get the time elapse since boot more accurately 82and in an atomic manner. 83The 84.Va boottime 85variable may be read and written without special precautions. 86.Sh SEE ALSO 87.Xr clock_settime 2 , 88.Xr ntp_adjtime 2 , 89.Xr settimeofday 2 , 90.Xr bintime 9 , 91.Xr binuptime 9 , 92.Xr getbintime 9 , 93.Xr getbinuptime 9 , 94.Xr getmicrotime 9 , 95.Xr getmicrouptime 9 , 96.Xr getnanotime 9 , 97.Xr getnanouptime 9 , 98.Xr microtime 9 , 99.Xr microuptime 9 , 100.Xr nanotime 9 , 101.Xr nanouptime 9 102.Rs 103.%A "Poul-Henning Kamp" 104.%T "Timecounters: Efficient and precise timekeeping in SMP kernels" 105.%J "Proceedings of EuroBSDCon 2002, Amsterdam" 106.%O /usr/share/doc/papers/timecounter.ascii.gz 107.Re 108.Rs 109.%A "Marshall Kirk McKusick" 110.%A "George V. Neville-Neil" 111.%B "The Design and Implementation of the FreeBSD Operating System" 112.%D "July 2004" 113.%I "Addison-Wesley" 114.%P "57-61,65-66" 115.Re 116