1.\" $NetBSD: adjtime.2,v 1.5 1995/10/12 15:40:44 jtc Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)adjtime.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt ADJTIME 2 38.Os BSD 4.3 39.Sh NAME 40.Nm adjtime 41.Nd "correct the time to allow synchronization of the system clock" 42.Sh SYNOPSIS 43.Fd #include <sys/time.h> 44.Ft int 45.Fn adjtime "const struct timeval *delta" "struct timeval *olddelta" 46.Sh DESCRIPTION 47.Fn Adjtime 48makes small adjustments to the system time, as returned by 49.Xr gettimeofday 2 , 50advancing or retarding it 51by the time specified by the timeval 52.Fa delta . 53If 54.Fa delta 55is negative, the clock is 56slowed down by incrementing it more slowly than normal until 57the correction is complete. 58If 59.Fa delta 60is positive, a larger increment than normal 61is used. 62The skew used to perform the correction is generally a fraction of one percent. 63Thus, the time is always 64a monotonically increasing function. 65A time correction from an earlier call to 66.Fn adjtime 67may not be finished when 68.Fn adjtime 69is called again. 70If 71.Fa olddelta 72is non-nil, 73the structure pointed to will contain, upon return, the 74number of microseconds still to be corrected 75from the earlier call. 76.Pp 77This call may be used by time servers that synchronize the clocks 78of computers in a local area network. 79Such time servers would slow down the clocks of some machines 80and speed up the clocks of others to bring them to the average network time. 81.Pp 82The call 83.Fn adjtime 84is restricted to the super-user. 85.Sh RETURN VALUES 86A return value of 0 indicates that the call succeeded. 87A return value of -1 indicates that an error occurred, and in this 88case an error code is stored in the global variable 89.Va errno . 90.Sh ERRORS 91.Fn Adjtime 92will fail if: 93.Bl -tag -width Er 94.It Bq Er EFAULT 95An argument points outside the process's allocated address space. 96.It Bq Er EPERM 97The process's effective user ID is not that of the super-user. 98.El 99.Sh SEE ALSO 100.Xr date 1 , 101.Xr gettimeofday 2 , 102.Xr timed 8 , 103.Xr timedc 8 , 104.Rs 105.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD" 106.%A R. Gusella 107.%A S. Zatti 108.Re 109.Sh HISTORY 110The 111.Fn adjtime 112function call appeared in 113.Bx 4.3 . 114