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.\" $OpenBSD: microtime.9,v 1.19 2019/10/22 20:19:41 cheloha Exp $
.\" $NetBSD: microtime.9,v 1.2 1999/03/16 00:40:47 garbled Exp $
.\"
.\" Copyright (c) 1998 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Jeremy Cooper.
.\"
.\" 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.
.\"
.\" 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.
.\"
.Dd $Mdocdate: October 22 2019 $
.Dt MICROTIME 9
.Os
.Sh NAME
.Nm microtime ,
.Nm getmicrotime ,
.Nm microuptime ,
.Nm getmicrouptime ,
.Nm microboottime ,
.Nm nanotime ,
.Nm getnanotime ,
.Nm nanouptime ,
.Nm getnanouptime ,
.Nm nanoboottime ,
.Nm bintime ,
.Nm binuptime ,
.Nm binboottime
.Nd system clocks
.Sh SYNOPSIS
.In sys/time.h
.Ft void
.Fo microtime
.Fa "struct timeval *tv"
.Fc
.Ft void
.Fo getmicrotime
.Fa "struct timeval *tv"
.Fc
.Ft void
.Fo microuptime
.Fa "struct timeval *tv"
.Fc
.Ft void
.Fo getmicrouptime
.Fa "struct timeval *tv"
.Fc
.Ft void
.Fo microboottime
.Fa "struct timeval *tv"
.Fc
.Ft void
.Fo nanotime
.Fa "struct timespec *tv"
.Fc
.Ft void
.Fo getnanotime
.Fa "struct timespec *tv"
.Fc
.Ft void
.Fo nanouptime
.Fa "struct timespec *tv"
.Fc
.Ft void
.Fo getnanouptime
.Fa "struct timespec *tv"
.Fc
.Ft void
.Fo nanoboottime
.Fa "struct timespec *tv"
.Fc
.Ft void
.Fo bintime
.Fa "struct bintime *tv"
.Fc
.Ft void
.Fo binuptime
.Fa "struct bintime *tv"
.Fc
.Ft void
.Fo binboottime
.Fa "struct bintime *tv"
.Fc
.Sh DESCRIPTION
This family of functions return different system clocks in various formats.
The "uptime" functions return the monotonically increasing time since boot.
The "boottime" functions return the UTC time at which the system booted.
The "time" functions return the current UTC time.
The various formats for the result are specified with:
.Bl -tag -offset indent -width "micro"
.It bin
result in struct bintime containing seconds and 64-bit fractions of seconds.
.It nano
result in struct timespec containing seconds and nanoseconds
.It micro
result in struct timeval containing seconds and microseconds
.El
.Pp
The functions with the "get" prefix return a less precise result, but much
faster.
They should be used where a precision of 10 msec is acceptable and where
performance is critical.
The functions without the "get" prefix return the best timestamp that can
be produced in the given format.
.Sh CODE REFERENCES
The implementation of these functions is partly machine dependent, but
the bulk of the code is in the file
.Pa sys/kern/kern_tc.c .
.Sh SEE ALSO
.Xr settimeofday 2 ,
.Xr hardclock 9 ,
.Xr hz 9 ,
.Xr inittodr 9 ,
.Xr time_second 9
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