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