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authorJacob McDonnell <jacob@jacobmcdonnell.com>2026-04-25 19:55:15 -0400
committerJacob McDonnell <jacob@jacobmcdonnell.com>2026-04-25 19:55:15 -0400
commit253e67c8b3a72b3a4757fdbc5845297628db0a4a (patch)
treeadf53b66087aa30dfbf8bf391a1dadb044c3bf4d /static/netbsd/man2/adjtime.2
parenta9157ce950dfe2fc30795d43b9d79b9d1bffc48b (diff)
docs: Added All NetBSD Manuals
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+.\" $NetBSD: adjtime.2,v 1.21 2015/12/07 23:20:57 pgoyette Exp $
+.\"
+.\" 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.
+.\"
+.\" @(#)adjtime.2 8.1 (Berkeley) 6/4/93
+.\"
+.Dd December 8, 2015
+.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
+.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
+If the calling user is not the super user, the
+.Fn adjtime
+system call will fail, and the
+.Fn adjtime
+function in the standard C library will try to use the
+.Xr clockctl 4
+device if present, thus making it possible for non privileged users to
+adjust the system time.
+If
+.Xr clockctl 4
+is not present or not accessible, then
+.Fn adjtime
+returns
+.Er EPERM .
+.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 clockctl 4 ,
+.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 .