freebsd-dev/lib/libc/sys/ntp_gettime.2

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.Dd June 21, 2003
.Dt NTP_GETTIME 2
.Os
.Sh NAME
.Nm ntp_gettime
.Nd NTP user application interface
.Sh SYNOPSIS
.In sys/timex.h
.Ft int
.Fn ntp_gettime "struct ntptimeval *ntv"
.Sh DESCRIPTION
The time returned by
.Fn ntp_gettime
is in a
.Vt timespec
structure, but may be in either microsecond
(seconds and microseconds) or nanosecond (seconds and nanoseconds) format.
The particular format in use is determined by the
.Dv STA_NANO
bit of the status
word returned by the
.Fn ntp_adjtime
system call.
.Fn ntp_gettime
has as argument a pointer to the
.Vt ntptimeval
structure with the following members:
.Bd -literal
struct ntptimeval {
	struct timespec time;	/* current time (ns) (ro) */
	long maxerror;		/* maximum error (us) (ro) */
	long esterror;		/* estimated error (us) (ro) */
	long tai;		/* TAI-UTC offset */
	int time_state;		/* time status */
};
.Ed
.Pp
These are understood as:
.Bl -tag -width ".Va time_state"
.It Va time
Current time (read-only).
.It Va maxerror
Maximum error in microseconds (read-only).
.It Va esterror
Estimated error in microseconds (read-only).
.It Va tai
Offset in seconds between the TAI and UTC time scales.
This offset is published twice a year and is an integral number of
seconds between TAI (which does not have leap seconds) and UTC (which
does).
.Xr ntpd 8 
or some other agent maintains this value.
A value of 0 means unknown.
As of the date of the manual page, the offset is 32 seconds.
.It Va time_state
Current time status.
.El
.Sh RETURN VALUES
.Rv -std ntp_gettime
.Pp
Possible states of the clock are:
.Pp
.Bl -tag -compact -width ".Dv TIME_ERROR"
.It Dv TIME_OK
Everything okay, no leap second warning.
.It Dv TIME_INS
Positive leap second warning.
At the end of the day, an additional second will be inserted after 23:59:59.
.It Dv TIME_DEL
Negative leap second warning.
At the end of the day, 23:59:59 is skipped.
.It Dv TIME_OOP
Leap second in progress.
.It Dv TIME_WAIT
Leap second has occurred.
.It Dv TIME_ERROR
Clock not synchronized.
.El
.Sh SEE ALSO
.Xr ntp_adjtime 2 ,
.Xr ntpd 8 ,
.Dq Li http://www.bipm.fr/enus/5_Scientific/c_time/time_1.html ,
.Dq Li http://www.boulder.nist.gov/timefreq/general/faq.htm ,
.Dq Li ftp://time.nist.gov/pub/leap-seconds.list
.Sh AUTHORS
This manual page was written by
.An Tom Rhodes Aq trhodes@FreeBSD.org .