NetBSD/share/man/man9/inittodr.9

.\" $NetBSD: inittodr.9,v 1.12 2006/09/06 18:06:00 wiz Exp $
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.\" Copyright (c) 1994 Christopher G. Demetriou
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.Dd September 6, 2006
.Dt INITTODR 9
.Os
.Sh NAME
.Nm inittodr
.Nd initialize system time
.Sh SYNOPSIS
.Ft void
.Fn inittodr "time_t base"
.Sh DESCRIPTION
The
.Fn inittodr
function determines the time and sets the system clock.
It tries to pick the correct time using a set of heuristics that examine
the system's battery-backed clock and the time reported by the file
system, as given in
.Fa base .
Those heuristics include:
.Bl -bullet
.It
If the battery-backed clock has a valid time, and is not significantly
behind the time provided by
.Fa base ,
it is used.
.It
If the battery-backed clock does not have a valid time, or is significantly
behind the time provided in
.Fa base ,
and the time provided in
.Fa base
is within reason,
.Fa base
is used as the current time.
.It
If the battery-backed clock appears invalid, and
.Fa base
appears non-sensical or was not provided (was given as zero),
an arbitrary base (typically some time within the same year that
the kernel was last updated) will be used.
.El
.Pp
Once a system time has been determined, it is stored in the
.Va time
variable.
.Sh DIAGNOSTICS
The
.Fn inittodr
function prints diagnostic messages if it has trouble figuring
out the system time.
Conditions that can cause diagnostic messages to be printed include:
.Bl -bullet
.It
There is no battery-backed clock present on the system.
.It
The battery-backed clock's time appears nonsensical.
.It
The
.Fa base
time appears nonsensical.
.It
The
.Fa base
time and the battery-backed clock's time differ by a large amount.
.El
.Sh SEE ALSO
.Xr clock_ymdhms_to_secs 9 ,
.Xr resettodr 9 ,
.Xr time 9
.Sh BUGS
Some systems use heuristics for picking the correct time that are slightly
different.