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author | imp <imp@FreeBSD.org> | 2003-06-21 20:27:54 +0000 |
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committer | imp <imp@FreeBSD.org> | 2003-06-21 20:27:54 +0000 |
commit | 6731c07a2f9d713b7e4e988b79593ef147202372 (patch) | |
tree | 8283f09ddc76af36d8135e2f8f0bc4d5dd71c829 /lib/libc/sys | |
parent | 3b7c9bf6dafb1d0fecc578f5e8c48acadb617c17 (diff) | |
download | FreeBSD-src-6731c07a2f9d713b7e4e988b79593ef147202372.zip FreeBSD-src-6731c07a2f9d713b7e4e988b79593ef147202372.tar.gz |
Add clarifications about the information that ntp_gettime returns.
TAI is a timescale, just like UTC. The tai field returns the offset
between the two, and isn't really used for precision time keeping.
Explain in brief what a positive and a negative leap seconds are. Add
some URLs to very useful web pages about time and time keeping for
more information on using this API.
Reviewed by: phk
Diffstat (limited to 'lib/libc/sys')
-rw-r--r-- | lib/libc/sys/ntp_gettime.2 | 26 |
1 files changed, 18 insertions, 8 deletions
diff --git a/lib/libc/sys/ntp_gettime.2 b/lib/libc/sys/ntp_gettime.2 index 7de0fed..a9b1f43 100644 --- a/lib/libc/sys/ntp_gettime.2 +++ b/lib/libc/sys/ntp_gettime.2 @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd April 1, 2003 +.Dd June 21, 2003 .Dt NTP_GETTIME 2 .Os .Sh NAME @@ -57,7 +57,7 @@ struct ntptimeval { struct timespec time; /* current time (ns) (ro) */ long maxerror; /* maximum error (us) (ro) */ long esterror; /* estimated error (us) (ro) */ - long tai; /* TAI offset */ + long tai; /* TAI-UTC offset */ int time_state; /* time status */ }; .Ed @@ -71,9 +71,14 @@ Maximum error in microseconds (read-only). .It Va esterror Estimated error in microseconds (read-only). .It Va tai -Temps Atomique International (French for International Atomic Time), -measures real time. -Used for acute time measurements. +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 @@ -86,9 +91,11 @@ Possible states of the clock are: .It Dv TIME_OK Everything okay, no leap second warning. .It Dv TIME_INS -Insert leap second warning. +Positive leap second warning. +At the end of the day, an additional second will be inserted after 23:59:59. .It Dv TIME_DEL -Delete leap second warning. +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 @@ -98,7 +105,10 @@ Clock not synchronized. .El .Sh SEE ALSO .Xr ntp_adjtime 2 , -.Xr ntpd 8 +.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 . |