09fd542e60
the netbsd versions, and tweaked by me with suggestions from phk. Reviewed by: phk Approved by: re@
323 lines
9.4 KiB
Groff
323 lines
9.4 KiB
Groff
.\" $NetBSD: ntp_adjtime.2,v 1.6 2003/04/16 13:34:55 wiz Exp $
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.\"
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.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Thomas Klausner.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 13, 2005
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.Dt NTP_ADJTIME 2
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.Os
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.Sh NAME
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.Nm ntp_adjtime ,
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.Nm ntp_gettime
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.Nd Network Time Protocol (NTP) daemon interface system calls
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/timex.h
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.Ft int
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.Fn ntp_adjtime "struct timex *"
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.Ft int
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.Fn ntp_gettime "struct ntptimeval *"
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.Sh DESCRIPTION
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The two system calls
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.Fn ntp_adjtime
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and
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.Fn ntp_gettime
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are the kernel interface to the Network Time Protocol (NTP) daemon
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.Xr ntpd 8 .
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.Pp
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The
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.Fn ntp_adjtime
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function is used by the NTP daemon to adjust the system clock to an
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externally derived time.
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The time offset and related variables which are set by
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.Fn ntp_adjtime
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are used by
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.Fn hardclock
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to adjust the phase and frequency of the phase- or frequency-lock loop
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(PLL resp. FLL) which controls the system clock.
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.Pp
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The
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.Fn ntp_gettime
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function provides the time, maximum error (sync distance) and
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estimated error (dispersion) to client user application programs.
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.Pp
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In the following, all variables that refer PPS are only relevant if
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the
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.Em PPS_SYNC
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option is enabled in the kernel.
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.Pp
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.Fn ntp_adjtime
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has as argument a
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.Va struct timex *
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of the following form:
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.Bd -literal
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struct timex {
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unsigned int modes; /* clock mode bits (wo) */
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long offset; /* time offset (us) (rw) */
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long freq; /* frequency offset (scaled ppm) (rw) */
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long maxerror; /* maximum error (us) (rw) */
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long esterror; /* estimated error (us) (rw) */
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int status; /* clock status bits (rw) */
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long constant; /* pll time constant (rw) */
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long precision; /* clock precision (us) (ro) */
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long tolerance; /* clock frequency tolerance (scaled
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* ppm) (ro) */
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/*
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* The following read-only structure members are implemented
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* only if the PPS signal discipline is configured in the
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* kernel.
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*/
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long ppsfreq; /* pps frequency (scaled ppm) (ro) */
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long jitter; /* pps jitter (us) (ro) */
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int shift; /* interval duration (s) (shift) (ro) */
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long stabil; /* pps stability (scaled ppm) (ro) */
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long jitcnt; /* jitter limit exceeded (ro) */
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long calcnt; /* calibration intervals (ro) */
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long errcnt; /* calibration errors (ro) */
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long stbcnt; /* stability limit exceeded (ro) */
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};
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.Ed
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.Pp
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The members of this struct have the following meanings when used as
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argument for
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.Fn ntp_adjtime :
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.Bl -tag -width tolerance -compact
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.It Fa modes
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Defines what settings should be changed with the current
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.Fn ntp_adjtime
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call (write-only).
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Bitwise OR of the following:
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.Bl -tag -width MOD_TIMECONST -compact -offset indent
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.It MOD_OFFSET
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set time offset
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.It MOD_FREQUENCY
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set frequency offset
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.It MOD_MAXERROR
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set maximum time error
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.It MOD_ESTERROR
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set estimated time error
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.It MOD_STATUS
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set clock status bits
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.It MOD_TIMECONST
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set PLL time constant
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.It MOD_CLKA
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set clock A
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.It MOD_CLKB
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set clock B
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.El
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.It Fa offset
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Time offset (in microseconds), used by the PLL/FLL to adjust the
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system time in small increments (read-write).
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.It Fa freq
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Frequency offset (scaled ppm) (read-write).
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.It Fa maxerror
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Maximum error (in microseconds).
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Initialized by an
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.Fn ntp_adjtime
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call, and increased by the kernel once each second to reflect the maximum
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error bound growth (read-write).
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.It Fa esterror
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Estimated error (in microseconds).
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Set and read by
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.Fn ntp_adjtime ,
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but unused by the kernel (read-write).
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.It Fa status
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System clock status bits (read-write).
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Bitwise OR of the following:
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.Bl -tag -width STA_PPSJITTER -compact -offset indent
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.It STA_PLL
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Enable PLL updates (read-write).
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.It STA_PPSFREQ
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Enable PPS freq discipline (read-write).
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.It STA_PPSTIME
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Enable PPS time discipline (read-write).
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.It STA_FLL
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Select frequency-lock mode (read-write).
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.It STA_INS
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Insert leap (read-write).
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.It STA_DEL
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Delete leap (read-write).
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.It STA_UNSYNC
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Clock unsynchronized (read-write).
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.It STA_FREQHOLD
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Hold frequency (read-write).
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.It STA_PPSSIGNAL
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PPS signal present (read-only).
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.It STA_PPSJITTER
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PPS signal jitter exceeded (read-only).
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.It STA_PPSWANDER
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PPS signal wander exceeded (read-only).
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.It STA_PPSERROR
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PPS signal calibration error (read-only).
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.It STA_CLOCKERR
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Clock hardware fault (read-only).
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.El
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.It Fa constant
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PLL time constant, determines the bandwidth, or
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.Dq stiffness ,
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of the PLL (read-write).
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.It Fa precision
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Clock precision (in microseconds).
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In most cases the same as the kernel tick variable (see
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.Xr hz 9 ) .
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If a precision clock counter or external time-keeping signal is available,
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it could be much lower (and depend on the state of the signal)
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(read-only).
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.It Fa tolerance
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Maximum frequency error, or tolerance of the CPU clock oscillator (scaled
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ppm).
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Ordinarily a property of the architecture, but could change under
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the influence of external time-keeping signals (read-only).
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.It Fa ppsfreq
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PPS frequency offset produced by the frequency median filter (scaled
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ppm) (read-only).
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.It Fa jitter
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PPS jitter measured by the time median filter in microseconds
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(read-only).
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.It Fa shift
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Logarithm to base 2 of the interval duration in seconds (PPS,
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read-only).
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.It Fa stabil
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PPS stability (scaled ppm); dispersion (wander) measured by the
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frequency median filter (read-only).
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.It Fa jitcnt
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Number of seconds that have been discarded because the jitter measured
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by the time median filter exceeded the limit
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.Em MAXTIME
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(PPS, read-only).
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.It Fa calcnt
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Count of calibration intervals (PPS, read-only).
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.It Fa errcnt
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Number of calibration intervals that have been discarded because the
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wander exceeded the limit
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.Em MAXFREQ
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or where the calibration interval jitter exceeded two ticks (PPS,
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read-only).
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.It Fa stbcnt
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Number of calibration intervals that have been discarded because the
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frequency wander exceeded the limit
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.Em MAXFREQ Ns /4
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(PPS, read-only).
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.El
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After the
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.Fn ntp_adjtime
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call, the
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.Va struct timex *
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structure contains the current values of the corresponding variables.
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.Pp
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.Fn ntp_gettime
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has as argument a
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.Va struct ntptimeval *
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with the following members:
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.Bd -literal
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struct ntptimeval {
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struct timeval time; /* current time (ro) */
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long maxerror; /* maximum error (us) (ro) */
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long esterror; /* estimated error (us) (ro) */
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};
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.Ed
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.Pp
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These have the following meaning:
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.Bl -tag -width tolerance -compact
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.It Fa time
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Current time (read-only).
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.It Fa maxerror
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Maximum error in microseconds (read-only).
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.It Fa esterror
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Estimated error in microseconds (read-only).
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.El
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.Sh RETURN VALUES
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.Fn ntp_adjtime
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and
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.Fn ntp_gettime
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return the current state of the clock on success, or any of the errors
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of
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.Xr copyin 9
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and
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.Xr copyout 9 .
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.Fn ntp_adjtime
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may additionally return
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.Er EPERM
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if the user calling
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.Fn ntp_adjtime
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does not have sufficient permissions.
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.Pp
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Possible states of the clock are:
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.Bl -tag -width TIME_ERROR -compact -offset indent
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.It TIME_OK
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Everything okay, no leap second warning.
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.It TIME_INS
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.Dq insert leap second
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warning.
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At the end of the day, a leap second will be inserted after 23:59:59.
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.It TIME_DEL
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.Dq delete leap second
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warning.
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At the end of the day, second 23:59:59 will be skipped.
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.It TIME_OOP
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Leap second in progress.
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.It TIME_WAIT
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Leap second has occurred within the last few seconds..
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.It TIME_ERROR
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Clock not synchronized.
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.El
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.Sh ERRORS
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The
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.Fn ntp_adjtime
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system call may return
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.Er EPERM
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if the caller
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does not have sufficient permissions.
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.Sh SEE ALSO
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.Xr options 4 ,
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.Xr ntpd 8 ,
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.Xr hardclock 9 ,
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.Xr hz 9
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.Bl -tag -width indent
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.It Pa http://www.bipm.fr/enus/5_Scientific/c_time/time_1.html
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.It Pa http://www.boulder.nist.gov/timefreq/general/faq.htm
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.It Pa ftp://time.nist.gov/pub/leap-seconds.list
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.El
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.Sh BUGS
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Take note that this
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.Tn API
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is extremely complex and stateful.
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Users should not attempt modification without first
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reviewing the
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.Xr ntpd 8
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sources in depth.
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