1.\" $NetBSD: microtime.9,v 1.12 2008/04/30 13:10:58 martin Exp $ 2.\" 3.\" Copyright (c) 1998 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Jeremy Cooper. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd September 14, 1998 31.Dt MICROTIME 9 32.Os 33.Sh NAME 34.Nm microtime 35.Nd realtime system clock 36.Sh SYNOPSIS 37.In sys/time.h 38.Ft void 39.Fo "microtime" 40.Fa "struct timeval *tv" 41.Fc 42.Sh DESCRIPTION 43.Fn microtime 44returns the current value of the system realtime clock in the structure 45pointed to by the argument 46.Fa tv . 47The system realtime clock is guaranteed to be monotonically increasing 48at all times. 49As such, 50all calls to 51.Fn microtime 52are guaranteed to return a system time greater than or equal to the 53system time returned in any previous calls. 54.Sh SEE ALSO 55.Xr settimeofday 2 , 56.Xr hardclock 9 , 57.Xr hz 9 , 58.Xr inittodr 9 , 59.Xr time_second 9 60.Sh CODE REFERENCES 61The implementation of the 62.Fn microtime 63function is machine dependent, 64hence its location in the source code tree varies from architecture to 65architecture. 66.Sh BUGS 67Despite the guarantee that the system realtime clock will always be 68monotonically increasing, 69it is always possible for the system clock to be manually reset by the 70system administrator to any date. 71