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tzselect: new options -c COORD and -n LIMIT

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These let the user select TZ based on geographical coordinates.
Combining '-c COORD' with '-t time' better insulates the user from
issues of nationality.
* tzselect.8 (SYNOPSIS, OPTIONS): Document the new options.
* tzselect.ksh: Implement them, using the great-circle special
case of the Vicenty formula for distances on ellipsoids.
(LC_ALL): Set to C, since tzselect is English only.  That way, we
treat decimal-points in -c option operands the same in all environments.
(usage): Document new options.  Document existing ones better.
(output_distances): New variable.
This commit is contained in:
Paul Eggert
2013-08-20 00:57:59 -07:00
parent 98cf55b78e
commit ebdf0c5d0c
2 changed files with 177 additions and 11 deletions
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26
tzselect.8
View File

@@ -4,6 +4,12 @@ tzselect \- select a time zone
.SH SYNOPSIS
.B tzselect
[
.B \-c
.I coord
] [
.B \-n
.I limit
] [
.B \-t
.I zonetabtype
] [
@@ -21,6 +27,26 @@ The output is suitable as a value for the TZ environment variable.
All interaction with the user is done via standard input and standard error.
.SH OPTIONS
.TP
.BI "\-c " coord
Instead of asking for continent and then country and then city,
ask for selection from time zones whose largest cities
are closest to the location with geographical coordinates
.IR coord .
Use ISO 6709 notation for
.IR coord ,
for example,
.B "\-c\ \+42.391415\-071.570419"
for 42.391415\(de\|N, 71.570419\(de\|W, and
.B "\-c\ +404226\-0740319"
for 48\(de\|42\(fm\|26\(sd\|N, 74\(de\|3\(fm\|19\(sd\|W.
.TP
.BI "\-n " limit
When
.B \-c
is used, display the closest
.I limit
locations (default 10).
.TP
.BI "\-t " zonetabtype
Make selections from the time zone table of type
.IR zonetabtype .

162
tzselect.ksh
View File

@@ -1,5 +1,7 @@
#!/bin/bash
export LC_ALL=C
PKGVERSION='(tzcode) '
TZVERSION=see_Makefile
REPORT_BUGS_TO=tz@iana.org
@@ -41,15 +43,43 @@ ZONETABTYPE=zone
exit 1
}
usage="Usage: tzselect [--version] [--help] [-t ZONETABTYPE]
coord=
location_limit=10
usage="Usage: tzselect [--version] [--help] [-c COORD] [-n LIMIT] [-t ZONETABTYPE]
Select a time zone interactively.
ZONETABTYPE should be one of 'time' or 'zone'.
Options:
-c COORD
Instead of asking for continent and then country and then city,
ask for selection from time zones whose largest cities
are closest to the location with geographical coordinates COORD.
COORD should use ISO 6709 notation, for example, '-c +4852+00220'
for Paris.
-n LIMIT
Display at most LIMIT locations when -c is used (default $location_limit).
-t ZONETABTYPE
Use time zone table ZONETABTYPE. ZONETABTYPE should be one of
'time' or 'zone'.
--version
Output version information.
--help
Output this help.
Report bugs to $REPORT_BUGS_TO."
while getopts t:-: opt
while getopts c:n:t:-: opt
do
case $opt$OPTARG in
c*)
coord=$OPTARG ;;
n*)
location_limit=$OPTARG ;;
t*)
ZONETABTYPE=$OPTARG ;;
-help)
@@ -90,6 +120,66 @@ case $(echo 1 | (select x in x; do break; done) 2>/dev/null) in
?*) PS3=
esac
# Awk script to read a time zone table and output the same table,
# with each column preceded by its distance from 'here'.
output_distances='
BEGIN {
FS = "\t"
while (getline <TZ_COUNTRY_TABLE)
if ($0 ~ /^[^#]/)
country[$1] = $2
country["US"] = "US" # Otherwise the strings get too long.
}
function cvt1(coord, deg, min, ilen, sign, sec) {
ilen = length(coord)
sign = substr(coord, 1, 1)
if (coord ~ /\./) {
deg = coord + 0
} else {
if (ilen <= 6) {
sec = 0
} else {
sec = sign substr(coord, ilen - 1)
ilen -= 2
}
min = sign substr(coord, ilen - 1, 2)
deg = substr(coord, 1, ilen - 2)
deg = (deg * 3600.0 + min * 60.0 + sec) / 3600.0
}
return deg * 0.017453292519943295
}
function convert_latitude(coord) {
match(coord, /..*[-+]/)
return cvt1(substr(coord, 1, RLENGTH - 1))
}
function convert_longitude(coord) {
match(coord, /..*[-+]/)
return cvt1(substr(coord, RLENGTH))
}
# Great-circle distance between points with given latitude and longitude.
# Inputs and output are in radians. This uses the great-circle special
# case of the Vicenty formula for distances on ellipsoids.
function dist(lat1, long1, lat2, long2, dlong, x, y, num, denom) {
dlong = long2 - long1
x = cos (lat2) * sin (dlong)
y = cos (lat1) * sin (lat2) - sin (lat1) * cos (lat2) * cos (dlong)
num = sqrt (x * x + y * y)
denom = sin (lat1) * sin (lat2) + cos (lat1) * cos (lat2) * cos (dlong)
return atan2(num, denom)
}
BEGIN {
coord_lat = convert_latitude(coord)
coord_long = convert_longitude(coord)
}
/^[^#]/ {
here_lat = convert_latitude($2)
here_long = convert_longitude($2)
line = $1 "\t" $2 "\t" $3 "\t" country[$1]
if (NF == 4)
line = line " - " $4
printf "%g\t%s\n", dist(coord_lat, coord_long, here_lat, here_long), line
}
'
# Begin the main loop. We come back here if the user wants to retry.
while
@@ -101,10 +191,14 @@ while
country=
region=
case $coord in
?*)
continent=coord;;
'')
# Ask the user for continent or ocean.
echo >&2 'Please select a continent or ocean.'
echo >&2 'Please select a continent, ocean, "coord", or "TZ".'
select continent in \
Africa \
@@ -117,7 +211,8 @@ while
Europe \
'Indian Ocean' \
'Pacific Ocean' \
'none - I want to specify the time zone using the Posix TZ format.'
'coord - I want to use geographical coordinates.' \
'TZ - I want to specify the time zone using the Posix TZ format.'
do
case $continent in
'')
@@ -130,10 +225,12 @@ while
break
esac
done
esac
case $continent in
'')
exit 1;;
none)
TZ)
# Ask the user for a Posix TZ string. Check that it conforms.
while
echo >&2 'Please enter the desired value' \
@@ -158,6 +255,45 @@ while
done
TZ_for_date=$TZ;;
*)
case $continent in
coord)
case $coord in
'')
echo >&2 'Please enter coordinates' \
'in ISO 6709 notation.'
echo >&2 'For example, +4042-07403 stands for'
echo >&2 '40 degrees 42 minutes north,' \
'74 degrees 3 minutes west.'
read coord;;
esac
distance_table=$($AWK \
-v coord="$coord" \
-v TZ_COUNTRY_TABLE="$TZ_COUNTRY_TABLE" \
"$output_distances" <$TZ_ZONE_TABLE |
sort -n |
sed "${location_limit}q"
)
regions=$(echo "$distance_table" | $AWK '
BEGIN { FS = "\t" }
{ print $NF }
')
echo >&2 'Please select one of the following' \
'time zone regions,'
echo >&2 'listed roughly in increasing order' \
"of distance from $coord".
select region in $regions
do
case $region in
'') echo >&2 'Please enter a number in range.';;
?*) break;;
esac
done
TZ=$(echo "$distance_table" | $AWK -v region="$region" '
BEGIN { FS="\t" }
$NF == region { print $4 }
')
;;
*)
# Get list of names of countries in the continent or ocean.
countries=$($AWK -F'\t' \
-v continent="$continent" \
@@ -185,7 +321,8 @@ while
# If there's more than one country, ask the user which one.
case $countries in
*"$newline"*)
echo >&2 'Please select a country.'
echo >&2 'Please select a country' \
'whose clocks agree with yours.'
select country in $countries
do
case $country in
@@ -256,6 +393,7 @@ while
}
$1 == cc && $4 == region { print $3 }
' <$TZ_ZONE_TABLE)
esac
# Make sure the corresponding zoneinfo file exists.
TZ_for_date=$TZDIR/$TZ
@@ -292,9 +430,11 @@ Universal Time is now: $UTdate."
echo >&2 ""
echo >&2 "The following information has been given:"
echo >&2 ""
case $country+$region in
?*+?*) echo >&2 " $country$newline $region";;
?*+) echo >&2 " $country";;
case $country%$region%$coord in
?*%?*%) echo >&2 " $country$newline $region";;
?*%%) echo >&2 " $country";;
%?*%?*) echo >&2 " coord $coord$newline $region";;
%%?*) echo >&2 " coord $coord";;
+) echo >&2 " TZ='$TZ'"
esac
echo >&2 ""
@@ -313,7 +453,7 @@ Universal Time is now: $UTdate."
'') exit 1;;
Yes) break
esac
do :
do coord=
done
case $SHELL in