[tz] [PATCH] tzselect: new options -c COORD and -n LIMIT
Paul Eggert
eggert at cs.ucla.edu
Tue Aug 20 08:01:02 UTC 2013
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.
---
tzselect.8 | 26 ++++++++++
tzselect.ksh | 162 +++++++++++++++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 177 insertions(+), 11 deletions(-)
diff --git a/tzselect.8 b/tzselect.8
index b5e2c88..884af36 100644
--- a/tzselect.8
+++ b/tzselect.8
@@ -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 .
diff --git a/tzselect.ksh b/tzselect.ksh
index dc9f256..da6adb2 100644
--- a/tzselect.ksh
+++ b/tzselect.ksh
@@ -1,5 +1,7 @@
#!/bin/bash
+export LC_ALL=C
+
PKGVERSION='(tzcode) '
TZVERSION=see_Makefile
REPORT_BUGS_TO=tz at 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
--
1.8.1.2
More information about the tz
mailing list