.\" Copyright (c) 2000 Kelly Yancey .\" 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. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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. .\" .\" $FreeBSD: src/share/man/man9/microtime.9,v 1.2.2.3 2001/12/17 11:30:18 ru Exp $ .\" $DragonFly: src/share/man/man9/microtime.9,v 1.4 2007/05/17 08:19:02 swildner Exp $ .\" .Dd January 3, 2000 .Dt MICROTIME 9 .Os .Sh NAME .Nm microtime , .Nm getmicrotime , .Nm nanotime , .Nm getnanotime .Nd get the current time .Sh SYNOPSIS .In sys/time.h .Ft void .Fn microtime "struct timeval *tv" .Ft void .Fn getmicrotime "struct timeval *tv" .Ft void .Fn nanotime "struct timespec *ts" .Ft void .Fn getnanotime "struct timespec *tsp" .Sh DESCRIPTION The .Fn microtime and .Fn getmicrotime functions stores the system time as a .Ft struct timeval at the address specified by .Fa tv . The .Fn nanotime and .Fn getnanotime functions perform the same utility, but record the time as a .Ft struct timespec instead. .Pp .Fn Microtime and .Fn nanotime always query the timecounter to return the current time as precisely as possible. Whereas .Fn getmicrotime and .Fn getnanotime functions are abstractions which can alternately return a less precise, but faster to obtain, time. This behaviour can be toggled via the kern.timecounter.method sysctl variable: .Bl -tag -width ABC .It Dv 0 sacrifice precision in favor of faster code execution .It Dv 1 return the more precise time (the same as calling .Fn microtime or .Fn nanotime ) . .El .Pp The intent of the .Fn getmicrotime and .Fn getnanotime functions is to enforce the user's preference for timer accuracy versus execution time. .Sh DIAGNOSTICS Buggy hardware can cause "calcru negative..." when kern.timecounter.method is set to 0. .Sh SEE ALSO .Xr getmicrouptime 9 , .Xr getnanouptime 9 , .Xr microuptime 9 , .Xr nanouptime 9 , .Xr tvtohz 9 .Sh HISTORY The .Nm and .Nm nanotime functions first appeared in .Fx 3.0 but existed in other incarnations since .Bx 4.4 .Sh AUTHORS This manual page was written by .An Kelly Yancey Aq kbyanc@posi.net .