Copyright (c) 1998 The NetBSD Foundation, Inc.
All rights reserved.
This code is derived from software contributed to The NetBSD Foundation
by Jeremy Cooper.
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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.
THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
``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 FOUNDATION OR CONTRIBUTORS
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.
Copyright (c) 2000 Kelly Yancey
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modification, are permitted provided that the following conditions
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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.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
$FreeBSD: src/share/man/man9/microtime.9,v 1.11 2005/10/13 16:01:28 jhb Exp $
.Dd May 13, 2013 .Dt MICROTIME 9 .Os .Sh NAME .Nm bintime , .Nm getbintime , .Nm microtime , .Nm getmicrotime , .Nm nanotime , .Nm getnanotime .Nd get the current time .Sh SYNOPSIS n sys/time.h .Ft void .Fo bintime .Fa "struct bintime *bt" .Fc .Ft void .Fo getbintime .Fa "struct bintime *bt" .Fc .Ft void .Fo "microtime" .Fa "struct timeval *tv" .Fc .Ft void .Fo getmicrotime .Fa "struct timeval *tv" .Fc .Ft void .Fo nanotime .Fa "struct timespec *tsp" .Fc .Ft void .Fo getnanotime .Fa "struct timespec *tsp" .Fc .Sh DESCRIPTION The .Fn bintime and .Fn getbintime functions store the system time as a .Vt "struct bintime" at the addresses specified by .Fa bt . The .Fn microtime and .Fn getmicrotime functions perform the same utility, but record the time as a .Vt "struct timeval" instead. Similarly the .Fn nanotime and .Fn getnanotime functions store the time as a .Vt "struct timespec" . The structures are described in .Xr timeval 3 .
p The .Fn bintime , .Fn microtime , and .Fn nanotime functions always query the timecounter to return the current time as precisely as possible. Whereas .Fn getbintime , .Fn getmicrotime , and .Fn getnanotime functions are abstractions which return a less precise, but faster to obtain, time.
p The intent of the .Fn getbintime , .Fn getmicrotime , and .Fn getnanotime functions is to enforce the user's preference for timer accuracy versus execution time. They should be used where a precision of
f 1/ Em HZ (e.g., 10 msec on a
f 100 Em HZ machine, see .Xr hz 9 ) is acceptable or where performance is priority.
p The system realtime clock is guaranteed to be monotonically increasing at all times. As such, all calls to these functions are guaranteed to return a system time greater than or equal to the system time returned in any previous calls. Comparable functions exist to retrieve the time elapsed since boot; see .Xr microuptime 9 . .Sh CODE REFERENCES The implementation of the .Fn microtime family of functions is in
a sys/kern/kern_tc.c as a part of the .Xr timecounter 9 framework.
p The implementation of the time counter sources used by the .Xr timecounter 9 is machine dependent, hence its location in the source code tree varies from architecture to architecture. .Sh SEE ALSO .Xr settimeofday 2 , .Xr bintime_add 9 , .Xr inittodr 9 , .Xr time_second 9 , .Xr tvtohz 9 .Sh AUTHORS This manual page was written by .An Jeremy Cooper and .An Kelly Yancey Aq Mt kbyanc@posi.net . .Sh CAVEATS Despite the guarantee that the system realtime clock will always be monotonically increasing, it is always possible for the system clock to be manually reset by the system administrator to any date.