113 lines
3.8 KiB
Groff
113 lines
3.8 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
|
|
.\" The Regents of the University of California. 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.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
|
|
.\"
|
|
.\" @(#)adjtime.2 8.1 (Berkeley) 6/4/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd June 4, 1993
|
|
.Dt ADJTIME 2
|
|
.Os BSD 4.3
|
|
.Sh NAME
|
|
.Nm adjtime
|
|
.Nd "correct the time to allow synchronization of the system clock"
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/time.h>
|
|
.Ft int
|
|
.Fn adjtime "const struct timeval *delta" "struct timeval *olddelta"
|
|
.Sh DESCRIPTION
|
|
.Fn Adjtime
|
|
makes small adjustments to the system time, as returned by
|
|
.Xr gettimeofday 2 ,
|
|
advancing or retarding it
|
|
by the time specified by the timeval
|
|
.Fa delta .
|
|
If
|
|
.Fa delta
|
|
is negative, the clock is
|
|
slowed down by incrementing it more slowly than normal until
|
|
the correction is complete.
|
|
If
|
|
.Fa delta
|
|
is positive, a larger increment than normal
|
|
is used.
|
|
The skew used to perform the correction is generally a fraction of one percent.
|
|
Thus, the time is always
|
|
a monotonically increasing function.
|
|
A time correction from an earlier call to
|
|
.Fn adjtime
|
|
may not be finished when
|
|
.Fn adjtime
|
|
is called again.
|
|
If
|
|
.Fa olddelta
|
|
is non-nil,
|
|
the structure pointed to will contain, upon return, the
|
|
number of microseconds still to be corrected
|
|
from the earlier call.
|
|
.Pp
|
|
This call may be used by time servers that synchronize the clocks
|
|
of computers in a local area network.
|
|
Such time servers would slow down the clocks of some machines
|
|
and speed up the clocks of others to bring them to the average network time.
|
|
.Pp
|
|
The call
|
|
.Fn adjtime
|
|
is restricted to the super-user.
|
|
.Sh RETURN VALUES
|
|
A return value of 0 indicates that the call succeeded.
|
|
A return value of -1 indicates that an error occurred, and in this
|
|
case an error code is stored in the global variable
|
|
.Va errno .
|
|
.Sh ERRORS
|
|
.Fn Adjtime
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EFAULT
|
|
An argument points outside the process's allocated address space.
|
|
.It Bq Er EPERM
|
|
The process's effective user ID is not that of the super-user.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr date 1 ,
|
|
.Xr gettimeofday 2 ,
|
|
.Xr timed 8 ,
|
|
.Xr timedc 8
|
|
.Rs
|
|
.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
|
|
.%A R. Gusella
|
|
.%A S. Zatti
|
|
.Re
|
|
.Sh HISTORY
|
|
The
|
|
.Fn adjtime
|
|
function call appeared in
|
|
.Bx 4.3 .
|