freebsd-src/lib/libsys/adjtime.2

.\" 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. 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.
.\"
.Dd May 13, 2021
.Dt ADJTIME 2
.Os
.Sh NAME
.Nm adjtime
.Nd "correct the time to allow synchronization of the system clock"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/time.h
.Ft int
.Fn adjtime "const struct timeval *delta" "struct timeval *olddelta"
.Sh DESCRIPTION
The
.Fn adjtime
system call
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 not a null pointer,
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
.Fn adjtime
system call
is restricted to the super-user.
.Sh RETURN VALUES
.Rv -std adjtime
.Sh ERRORS
The
.Fn adjtime
system call 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
.Rs
.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
.%A R. Gusella
.%A S. Zatti
.Re
.Sh HISTORY
The
.Fn adjtime
system call appeared in
.Bx 4.3 .
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" 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.`
Renumber copyright clause 4 Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96 2017-02-28 23:42:47 +00:00			`.\" 3. Neither the name of the University nor the names of its contributors`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" 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.`
			`.\"`
Remove references to timed(8) There are still references to timed(8) and timedc(8) in the base system, which were removed in 2018. PR: 255425 Reported by: Ceri Davies <ceri at submonkey dot net> Reviewed by: ygy, gbe MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D30232 2021-05-13 07:53:08 +00:00			`.Dd May 13, 2021`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Dt ADJTIME 2`
mdoc(7) police: removed HISTORY info from the .Os call. 2001-07-10 13:41:46 +00:00			`.Os`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh NAME`
			`.Nm adjtime`
			`.Nd "correct the time to allow synchronization of the system clock"`
Introduce ".Lb" macro to libc manpages. More libraries manpages updates following. 2000-04-21 09:42:15 +00:00			`.Sh LIBRARY`
			`.Lb libc`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh SYNOPSIS`
mdoc(7) police: Use the new .In macro for #include statements. 2001-10-01 16:09:29 +00:00			`.In sys/time.h`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Ft int`
Fixed missing const(s) or #include(s) in synopsis. 1997-04-11 18:47:10 +00:00			`.Fn adjtime "const struct timeval delta" "struct timeval olddelta"`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh DESCRIPTION`
The .Fn function 2002-07-15 20:50:16 +00:00			`The`
			`.Fn adjtime`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`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`
``NULL is a specific instance of a null pointer constant; the generic is a "null pointer".'' Making good use of the excellent explanations sent to me by Ruslan Ermilov, Garrett Wollman and Bruce Evans, correct the descriptions of null pointers. They are just "null pointers", not nil, not NULL or ".Dv NULL". Suggested by: ru, wollman, bde Reviewed by: ru, wollman Pointy hat: keramida 2004-12-23 23:45:25 +00:00			`is not a null pointer,`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`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`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`The`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Fn adjtime`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`is restricted to the super-user.`
			`.Sh RETURN VALUES`
Use the ``.Rv -std'' mdoc(7) macro in appropriate cases. Reviewed by: ru 2001-08-09 13:32:13 +00:00			`.Rv -std adjtime`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh ERRORS`
The .Fn function 2002-07-15 20:50:16 +00:00			`The`
			`.Fn adjtime`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call will fail if:`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.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 ,`
Remove references to timed(8) There are still references to timed(8) and timedc(8) in the base system, which were removed in 2018. PR: 255425 Reported by: Ceri Davies <ceri at submonkey dot net> Reviewed by: ygy, gbe MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D30232 2021-05-13 07:53:08 +00:00			`.Xr gettimeofday 2`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Rs`
			`.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"`
			`.%A R. Gusella`
			`.%A S. Zatti`
			`.Re`
			`.Sh HISTORY`
			`The`
Update a bunch of man pages to use .Fn instead of .Nm when referencing funciton names. 1996-08-22 22:05:59 +00:00			`.Fn adjtime`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call appeared in`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Bx 4.3 .`