NTP_ADJTIME(2) BSD System Calls Manual NTP_ADJTIME(2)NAMEntp_adjtime — NTP daemon application interface
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <sys/timex.h>
int
ntp_adjtime(struct timex *tp);
DESCRIPTION
The ntp_adjtime() system call is used as a kernel interface for the Net‐
work Time Protocol daemon, ntpd(8). Certain fields of the timex struc‐
ture are interpreted in either microseconds or nanoseconds, according to
the state of the STA_NANO bit in the status word.
In the DragonFly kernel, the ntp_adjtime() and ntp_gettime(2) system
calls can be used to determine which resolution is in use, and to select
either one at any time. The resolution selected affects the scaling of
certain fields in the ntp_gettime() and ntp_adjtime() system calls.
Take note that this API is extremely complex and stateful. Users should
not attempt modification without first reviewing the ntpd(8) sources in
depth.
/*
* NTP daemon interface (ntp_adjtime()) - used to discipline CPU clock
* oscillator and determine status.
*
* Note: The offset, precision and jitter members are in microseconds if
* STA_NANO is zero and nanoseconds if not.
*/
struct timex {
unsigned int modes; /* clock mode bits (wo) */
long offset; /* time offset (ns/us) (rw) */
long freq; /* frequency offset (scaled PPM) (rw) */
long maxerror; /* maximum error (us) (rw) */
long esterror; /* estimated error (us) (rw) */
int status; /* clock status bits (rw) */
long constant; /* poll interval (log2 s) (rw) */
long precision; /* clock precision (ns/us) (ro) */
long tolerance; /* clock frequency tolerance (scaled
* PPM) (ro) */
/*
* The following read-only structure members are implemented
* only if the PPS signal discipline is configured in the
* kernel. They are included in all configurations to insure
* portability.
*/
long ppsfreq; /* PPS frequency (scaled PPM) (ro) */
long jitter; /* PPS jitter (ns/us) (ro) */
int shift; /* interval duration (s) (shift) (ro) */
long stabil; /* PPS stability (scaled PPM) (ro) */
long jitcnt; /* jitter limit exceeded (ro) */
long calcnt; /* calibration intervals (ro) */
long errcnt; /* calibration errors (ro) */
long stbcnt; /* stability limit exceeded (ro) */
};
Upon successful completion, ntp_adjtime() will fill the tp argument with
the current clock state.
RETURN VALUES
The ntp_adjtime() function returns the value 0 if successful; otherwise
the value -1 is returned and the global variable errno is set to indicate
the error.
Possible states of the clock are:
TIME_OK Everything okay, no leap second warning.
TIME_INS insert leap second warning.
TIME_DEL delete leap second warning.
TIME_OOP Leap second in progress.
TIME_WAIT Leap second has occurred.
TIME_ERROR Clock not synchronized.
ERRORS
The ntp_gettime() system call may return EPERM if the caller does not
have sufficient permissions.
SEE ALSOntp_gettime(2), ntpd(8) (pkgsrc/net/openntpd)
AUTHORS
This manual page was written by Tom Rhodes ⟨trhodes@FreeBSD.org⟩.
BSD April 1, 2003 BSD
