1.\" $NetBSD: inittodr.9,v 1.2 1996/03/27 21:16:06 jtc 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: src/share/man/man9/inittodr.9,v 1.4.2.4 2001/12/17 11:30:18 ru Exp $ 33.\" 34.Dd March 22, 1997 35.Dt INITTODR 9 36.Os 37.Sh NAME 38.Nm inittodr 39.Nd initialize system time 40.Sh SYNOPSIS 41.In sys/types.h 42.In sys/systm.h 43.Ft void 44.Fn inittodr "time_t base" 45.Sh DESCRIPTION 46The 47.Fn inittodr 48function determines the time and sets the system clock. 49It tries to pick the correct time using a set of heuristics that examine 50the system's battery backed clock and the time obtained from the root 51file system, as given in 52.Fa base . 53How the 54.Fa base 55value is obtained will vary depending on the 56root file system type. 57The heuristics used include: 58.Bl -bullet 59.It 60If the battery-backed clock has a valid time, it is used. 61.\" .It 62.\" If the battery-backed clock does not have a valid time, and 63.\" the time provided in 64.\" .Fa base 65.\" is within reason, 66.\" .Fa base 67.\" is used as the current time. 68.\" .It 69.\" If the battery-backed clock appears invalid, and 70.\" .Fa base 71.\" appears non-sensical or was not provided (was given as zero), 72.\" a arbitrary base (typically some time in the late 1970s) 73.\" will be used. 74.It 75If the battery-backed clock does not have a valid time, 76the time provided in 77.Fa base 78will be used. 79.El 80.Pp 81Once a system time has been determined, it is stored in the 82.Va time 83variable. 84.Sh DIAGNOSTICS 85The 86.Fn inittodr 87function prints diagnostic messages if it has trouble figuring 88out the system time. Conditions that can cause diagnostic 89messages to be printed include: 90.Bl -bullet 91.It 92The battery-backed clock's time appears nonsensical. 93.\" .It 94.\" The 95.\" .Fa base 96.\" time appears nonsensical. 97.\" .It 98.\" The 99.\" .Fa base 100.\" time and the battery-backed clock's time differ by a large amount. 101.El 102.Sh SEE ALSO 103.Xr resettodr 9 , 104.Xr time 9 105.Sh BUGS 106On many systems, 107.Fn inittodr 108has to convert from 109a time expressed in terms of year, month, day, hours, minutes, 110and seconds to 111.Va time , 112expressed in seconds. Many of the implementations could share code, 113but do not. 114.Pp 115Each system's heuristics for picking the correct time are slightly 116different. 117.Pp 118The 119.Fx 120implementation should do a better job of validating the time provided in 121.Fa base 122when the battery-backed clock is unusable. Currently it unconditionally 123sets the system clock to this value. 124