122 lines
3.5 KiB
Groff
122 lines
3.5 KiB
Groff
.\" $NetBSD: time.9,v 1.1 1995/11/25 21:24:53 perry Exp $
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.\"
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.\" Copyright (c) 1994 Christopher G. Demetriou
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Christopher G. Demetriou
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.\" for the NetBSD Project.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 17, 2004
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.Dt TIME 9
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.Os
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.Sh NAME
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.In sys/time.h
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.Nm boottime ,
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.Nm time_second ,
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.Nm time_uptime
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.Nd system time variables
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.Sh SYNOPSIS
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.Bl -item -compact
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.It
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.Va extern struct timeval boottime ;
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.It
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.Va extern struct time_t time_second ;
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.It
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.Va extern struct timeval time_uptime ;
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.El
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.Sh DESCRIPTION
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The
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.Va boottime
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variable holds the system boot time.
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.Pp
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The
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.Va time_second
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variable is the system's
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.Dq wall time
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clock to the second.
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.Pp
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The
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.Va time_uptime variable is the number of seconds since boot.
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.Pp
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The
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.Xr bintime 9,
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.Xr getbintime 9 ,
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.Xr microtime 9 ,
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.Xr getmicrotime 9 ,
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.Xr nanotime 9 ,
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and
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.Xr getnanotime 9 ,
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functions can be used to get the current time more accurately and in an
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atomic manner.
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Similarly, the
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The
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.Xr binuptime 9,
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.Xr getbinuptime 9 ,
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.Xr microuptime 9 ,
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.Xr getmicrouptime 9 ,
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.Xr nanouptime 9 ,
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and
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.Xr getnanouptime 9 ,
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functions can be used to get the time elapse since boot more accurately
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and in an atomic manner.
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The
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.Va boottime
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variable may be read and written without special precautions.
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.Pp
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.Sh SEE ALSO
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.Xr clock_settime 2 ,
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.Xr ntp_adjtime 2 ,
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.Xr settimeofday 2 ,
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.Xr getbintime 9 ,
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.Xr getbinuptime 9 ,
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.Xr getmicrotime 9 ,
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.Xr getmicrouptime 9 ,
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.Xr getnanotime 9 ,
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.Xr getnanouptime 9 ,
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.Xr bintime 9 ,
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.Xr binuptime 9 ,
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.Xr microtime 9 ,
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.Xr microuptime 9 ,
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.Xr nanotime 9,
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.Xr nanouptime 9
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.Rs
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.%A "Poul-Henning Kamp"
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.%T "Timecounters: Efficient and precise timekeeping in SMP kernels"
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.%J "Proceedings of EuroBSDCon 2002"
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.%C "Amsterdam"
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.%O /usr/share/doc/papers/timecounter.ascii.gz
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.Re
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.Rs
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.%A "Marshall Kirk McKusick"
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.%A "George V. Neville-Neil"
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.%B "The Design and Implementation of the FreeBSD Operating System"
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.%D "July 2004"
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.%I "Addison-Wesley"
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.%P "57-61,65-66"
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.Re
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