109 lines
3.6 KiB
Awk
109 lines
3.6 KiB
Awk
# Generate the 'leapseconds' file from 'leap-seconds.list'.
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# This file is in the public domain.
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BEGIN {
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print "# Allowance for leap seconds added to each time zone file."
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print ""
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print "# This file is in the public domain."
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print ""
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print "# This file is generated automatically from the data in the public-domain"
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print "# leap-seconds.list file, which can be copied from"
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print "# <ftp://ftp.nist.gov/pub/time/leap-seconds.list>"
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print "# or <ftp://ftp.boulder.nist.gov/pub/time/leap-seconds.list>"
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print "# or <ftp://tycho.usno.navy.mil/pub/ntp/leap-seconds.list>."
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print "# For more about leap-seconds.list, please see"
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print "# The NTP Timescale and Leap Seconds"
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print "# <https://www.eecis.udel.edu/~mills/leap.html>."
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print ""
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print "# The International Earth Rotation and Reference Systems Service"
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print "# periodically uses leap seconds to keep UTC to within 0.9 s of UT1"
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print "# (which measures the true angular orientation of the earth in space)"
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print "# and publishes leap second data in a copyrighted file"
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print "# <https://hpiers.obspm.fr/iers/bul/bulc/Leap_Second.dat>."
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print "# See: Levine J. Coordinated Universal Time and the leap second."
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print "# URSI Radio Sci Bull. 2016;89(4):30-6. doi:10.23919/URSIRSB.2016.7909995"
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print "# <https://ieeexplore.ieee.org/document/7909995>."
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print ""
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print "# There were no leap seconds before 1972, because the official mechanism"
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print "# accounting for the discrepancy between atomic time and the earth's rotation"
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print "# did not exist. The first (\"1 Jan 1972\") data line in leap-seconds.list"
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print "# does not denote a leap second; it denotes the start of the current definition"
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print"# of UTC."
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print ""
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print "# The correction (+ or -) is made at the given time, so lines"
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print "# will typically look like:"
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print "# Leap YEAR MON DAY 23:59:60 + R/S"
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print "# or"
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print "# Leap YEAR MON DAY 23:59:59 - R/S"
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print ""
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print "# If the leap second is Rolling (R) the given time is local time (unused here)."
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monthabbr[ 1] = "Jan"
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monthabbr[ 2] = "Feb"
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monthabbr[ 3] = "Mar"
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monthabbr[ 4] = "Apr"
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monthabbr[ 5] = "May"
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monthabbr[ 6] = "Jun"
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monthabbr[ 7] = "Jul"
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monthabbr[ 8] = "Aug"
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monthabbr[ 9] = "Sep"
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monthabbr[10] = "Oct"
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monthabbr[11] = "Nov"
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monthabbr[12] = "Dec"
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for (i in monthabbr) {
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monthnum[monthabbr[i]] = i
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monthlen[i] = 31
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}
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monthlen[2] = 28
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monthlen[4] = monthlen[6] = monthlen[9] = monthlen[11] = 30
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}
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/^#\tUpdated through/ || /^#\tFile expires on:/ {
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last_lines = last_lines $0 "\n"
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}
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/^#[$][ \t]/ { updated = $2 }
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/^#[@][ \t]/ { expires = $2 }
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/^#/ { next }
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{
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NTP_timestamp = $1
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TAI_minus_UTC = $2
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hash_mark = $3
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one = $4
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month = $5
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year = $6
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if (old_TAI_minus_UTC) {
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if (old_TAI_minus_UTC < TAI_minus_UTC) {
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sign = "23:59:60\t+"
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} else {
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sign = "23:59:59\t-"
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}
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m = monthnum[month] - 1
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if (m == 0) {
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year--;
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m = 12
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}
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month = monthabbr[m]
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day = monthlen[m]
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day += m == 2 && year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)
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printf "Leap\t%s\t%s\t%s\t%s\tS\n", year, month, day, sign
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}
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old_TAI_minus_UTC = TAI_minus_UTC
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}
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END {
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# The difference between the NTP and POSIX epochs is 70 years
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# (including 17 leap days), each 24 hours of 60 minutes of 60
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# seconds each.
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epoch_minus_NTP = ((1970 - 1900) * 365 + 17) * 24 * 60 * 60
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print ""
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print "# POSIX timestamps for the data in this file:"
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printf "#updated %s\n", updated - epoch_minus_NTP
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printf "#expires %s\n", expires - epoch_minus_NTP
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printf "\n%s", last_lines
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}
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