Replace the leap-seconds file in r347488 from USNO with a
leap-seconds file from NIST at ftp://ftp.nist.gov/pub/time. Future updates should use the NIST version of file, available at ftp://ftp.nist.gov/pub/time/leap-seconds.list . Requested by: ian@ Obtained from: ftp://ftp.nist.gov/pub/time/leap-seconds.3676924800 MFC after: 3 days
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svn path=/head/; revision=347606
@ -15,12 +15,17 @@
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# are transmitted by almost all time services.
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#
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# The first column shows an epoch as a number of seconds
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# since 1900.0 and the second column shows the number of
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# seconds that must be added to UTC to compute TAI for
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# any timestamp at or after that epoch. The value on
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# each line is valid from the indicated initial instant
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# until the epoch given on the next one or indefinitely
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# into the future if there is no next line.
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# since 1 January 1900, 00:00:00 (1900.0 is also used to
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# indicate the same epoch.) Both of these time stamp formats
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# ignore the complexities of the time scales that were
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# used before the current definition of UTC at the start
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# of 1972. (See note 3 below.)
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# The second column shows the number of seconds that
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# must be added to UTC to compute TAI for any timestamp
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# at or after that epoch. The value on each line is
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# valid from the indicated initial instant until the
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# epoch given on the next one or indefinitely into the
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# future if there is no next line.
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# (The comment on each line shows the representation of
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# the corresponding initial epoch in the usual
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# day-month-year format. The epoch always begins at
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@ -42,11 +47,11 @@
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# and can be ignored for many purposes. These differences
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# are tabulated in Circular T, which is published monthly
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# by the International Bureau of Weights and Measures
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# (BIPM). See www.bipm.fr for more information.
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# (BIPM). See www.bipm.org for more information.
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#
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# 3. The current defintion of the relationship between UTC
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# 3. The current definition of the relationship between UTC
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# and TAI dates from 1 January 1972. A number of different
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# time scales were in use before than epoch, and it can be
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# time scales were in use before that epoch, and it can be
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# quite difficult to compute precise timestamps and time
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# intervals in those "prehistoric" days. For more information,
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# consult:
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@ -56,23 +61,26 @@
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# or
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# Terry Quinn, "The BIPM and the Accurate Measurement
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# of Time," Proc. of the IEEE, Vol. 79, pp. 894-905,
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# July, 1991.
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# July, 1991. <http://dx.doi.org/10.1109/5.84965>
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# reprinted in:
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# Christine Hackman and Donald B Sullivan (eds.)
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# Time and Frequency Measurement
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# American Association of Physics Teachers (1996)
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# <http://tf.nist.gov/general/pdf/1168.pdf>, pp. 75-86
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#
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# 4. The insertion of leap seconds into UTC is currently the
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# responsibility of the International Earth Rotation Service,
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# which is located at the Paris Observatory:
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# 4. The decision to insert a leap second into UTC is currently
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# the responsibility of the International Earth Rotation and
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# Reference Systems Service. (The name was changed from the
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# International Earth Rotation Service, but the acronym IERS
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# is still used.)
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#
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# Central Bureau of IERS
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# 61, Avenue de l'Observatoire
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# 75014 Paris, France.
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# Leap seconds are announced by the IERS in its Bulletin C.
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#
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# Leap seconds are announced by the IERS in its Bulletin C
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# See www.iers.org for more details.
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#
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# See hpiers.obspm.fr or www.iers.org for more details.
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#
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# All national laboratories and timing centers use the
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# data from the BIPM and the IERS to construct their
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# local realizations of UTC.
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# Every national laboratory and timing center uses the
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# data from the BIPM and the IERS to construct UTC(lab),
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# their local realization of UTC.
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#
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# Although the definition also includes the possibility
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# of dropping seconds ("negative" leap seconds), this has
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@ -102,7 +110,7 @@
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#
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# If your system realizes the leap second by repeating 00:00:00 UTC twice
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# (this is possible but not usual), then the advance to the next entry
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# in the table must occur the second time that a time equivlent to
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# in the table must occur the second time that a time equivalent to
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# 00:00:00 UTC is used. Thus, using the same example as above:
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#
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# ...
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@ -112,7 +120,10 @@
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# ...
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#
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# in both cases the use of timestamps based on TAI produces a smooth
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# time scale with no discontinuity in the time interval.
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# time scale with no discontinuity in the time interval. However,
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# although the long-term behavior of the time scale is correct in both
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# methods, the second method is technically not correct because it adds
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# the extra second to the wrong day.
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#
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# This complexity would not be needed for negative leap seconds (if they
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# are ever used). The UTC time would skip 23:59:59 and advance from
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@ -121,14 +132,23 @@
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# with, since the difficulty of unambiguously representing the epoch
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# during the leap second does not arise.
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#
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# Questions or comments to:
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# Jeff Prillaman
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# Time Service Department
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# US Naval Observatory
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# Washington, DC
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# jeff.k.prillaman@navy.mil
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# Some systems implement leap seconds by amortizing the leap second
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# over the last few minutes of the day. The frequency of the local
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# clock is decreased (or increased) to realize the positive (or
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# negative) leap second. This method removes the time step described
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# above. Although the long-term behavior of the time scale is correct
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# in this case, this method introduces an error during the adjustment
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# period both in time and in frequency with respect to the official
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# definition of UTC.
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#
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# Last Update of leap second values: 28 Jan 2019
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# Questions or comments to:
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# Judah Levine
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# Time and Frequency Division
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# NIST
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# Boulder, Colorado
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# Judah.Levine@nist.gov
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#
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# Last Update of leap second values: 8 July 2016
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#
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# The following line shows this last update date in NTP timestamp
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# format. This is the date on which the most recent change to
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@ -136,7 +156,22 @@
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# be identified by the unique pair of characters in the first two
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# columns as shown below.
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#
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#$ 3757622400
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#$ 3676924800
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#
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# The NTP timestamps are in units of seconds since the NTP epoch,
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# which is 1 January 1900, 00:00:00. The Modified Julian Day number
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# corresponding to the NTP time stamp, X, can be computed as
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#
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# X/86400 + 15020
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#
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# where the first term converts seconds to days and the second
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# term adds the MJD corresponding to the time origin defined above.
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# The integer portion of the result is the integer MJD for that
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# day, and any remainder is the time of day, expressed as the
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# fraction of the day since 0 hours UTC. The conversion from day
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# fraction to seconds or to hours, minutes, and seconds may involve
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# rounding or truncation, depending on the method used in the
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# computation.
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#
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# The data in this file will be updated periodically as new leap
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# seconds are announced. In addition to being entered on the line
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@ -149,10 +184,11 @@
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# is announced.
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#
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# The following entry specifies the expiration date of the data
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# in this file in units of seconds since 1900.0. This expiration date
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# will be changed at least twice per year whether or not a new leap
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# second is announced. These semi-annual changes will be made no
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# later than 1 June and 1 December of each year to indicate what
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# in this file in units of seconds since the origin at the instant
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# 1 January 1900, 00:00:00. This expiration date will be changed
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# at least twice per year whether or not a new leap second is
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# announced. These semi-annual changes will be made no later
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# than 1 June and 1 December of each year to indicate what
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# action (if any) is to be taken on 30 June and 31 December,
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# respectively. (These are the customary effective dates for new
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# leap seconds.) This expiration date will be identified by a
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@ -168,10 +204,10 @@
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# current -- the update time stamp, the data and the name of the file
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# will not change.
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#
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# Updated through IERS Bulletin C 57
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# File expires on: 1 Dec 2019
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# Updated through IERS Bulletin C57
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# File expires on: 28 December 2019
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#
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#@ 3784147200
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#@ 3786480000
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#
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2272060800 10 # 1 Jan 1972
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2287785600 11 # 1 Jul 1972
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@ -205,7 +241,7 @@
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# the following special comment contains the
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# hash value of the data in this file computed
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# use the secure hash algorithm as specified
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# by FIPS 180-1. See the files in ~/sha for
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# by FIPS 180-1. See the files in ~/pub/sha for
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# the details of how this hash value is
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# computed. Note that the hash computation
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# ignores comments and whitespace characters
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@ -216,5 +252,4 @@
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# the hash line is also ignored in the
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# computation.
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#
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#h 630ac741 2fffdd6b 858a7d1d 31d4802f 6382e10c
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#
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#h 83c68138 d3650221 07dbbbcd 11fcc859 ced1106a
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