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 #! /bin/ksh

 # '@(#)tzselect.ksh	8.1'

 # Ask the user about the time zone, and output the resulting TZ value to stdout.

 # Interact with the user via stderr and stdin.

 # Contributed by Paul Eggert.

 # Porting notes:

 #

 # This script requires several features of the Korn shell.

 # If your host lacks the Korn shell,

 # you can use either of the following free programs instead:

 #

 #	<a href=ftp://ftp.gnu.org/pub/gnu/>

 #	Bourne-Again shell (bash)

 #	</a>

 #

 #	<a href=ftp://ftp.cs.mun.ca/pub/pdksh/pdksh.tar.gz>

 #	Public domain ksh

 #	</a>

 #

 # This script also uses several features of modern awk programs.

 # If your host lacks awk, or has an old awk that does not conform to Posix.2,

 # you can use either of the following free programs instead:

 #

 #	<a href=ftp://ftp.gnu.org/pub/gnu/>

 #	GNU awk (gawk)

 #	</a>

 #

 #	<a href=ftp://ftp.whidbey.net/pub/brennan/>

 #	mawk

 #	</a>

 # Specify default values for environment variables if they are unset.

 : ${AWK=awk}

 : ${TZDIR=$(pwd)}

 # Check for awk Posix compliance.

 ($AWK -v x=y 'BEGIN { exit 123 }') </dev/null >/dev/null 2>&1

 [ $? = 123 ] || {

 	echo >&2 "$0: Sorry, your \`$AWK' program is not Posix compatible."

 	exit 1

 }

 # Make sure the tables are readable.

 TZ_COUNTRY_TABLE=$TZDIR/iso3166.tab

 TZ_ZONE_TABLE=$TZDIR/zone.tab

 for f in $TZ_COUNTRY_TABLE $TZ_ZONE_TABLE

 do

 	<$f || {

 		echo >&2 "$0: time zone files are not set up correctly"

 		exit 1

 	}

 done

 newline='

 '

 IFS=$newline

 # Work around a bug in bash 1.14.7 and earlier, where $PS3 is sent to stdout.

 case $(echo 1 | (select x in x; do break; done) 2>/dev/null) in

 ?*) PS3=

 esac

 # Begin the main loop.  We come back here if the user wants to retry.

 while

 	echo >&2 'Please identify a location' \

 		'so that time zone rules can be set correctly.'

 	continent=

 	country=

 	region=

 	# Ask the user for continent or ocean.

 	echo >&2 'Please select a continent or ocean.'

 	select continent in \

 	    Africa \

 	    Americas \

 	    Antarctica \

 	    'Arctic Ocean' \

 	    Asia \

 	    'Atlantic Ocean' \

 	    Australia \

 	    Europe \

 	    'Indian Ocean' \

 	    'Pacific Ocean' \

 	    'none - I want to specify the time zone using the Posix TZ format.'

 	do

 	    case $continent in

 	    '')

 		echo >&2 'Please enter a number in range.';;

 	    ?*)

 		case $continent in

 		Americas) continent=America;;

 		*' '*) continent=$(expr "$continent" : '\([^ ]*\)')

 		esac

 		break

 	    esac

 	done

 	case $continent in

 	'')

 		exit 1;;

 	none)

 		# Ask the user for a Posix TZ string.  Check that it conforms.

 		while

 			echo >&2 'Please enter the desired value' \

 				'of the TZ environment variable.'

 			echo >&2 'For example, GST-10 is a zone named GST' \

 				'that is 10 hours ahead (east) of UTC.'

 			read TZ

 			$AWK -v TZ="$TZ" 'BEGIN {

 				tzname = "[^-+,0-9][^-+,0-9][^-+,0-9]+"

 				time = "[0-2]?[0-9](:[0-5][0-9](:[0-5][0-9])?)?"

 				offset = "[-+]?" time

 				date = "(J?[0-9]+|M[0-9]+\.[0-9]+\.[0-9]+)"

 				datetime = "," date "(/" time ")?"

 				tzpattern = "^(:.*|" tzname offset "(" tzname \

 				  "(" offset ")?(" datetime datetime ")?)?)$"

 				if (TZ ~ tzpattern) exit 1

 				exit 0

 			}'

 		do

 			echo >&2 "\`$TZ' is not a conforming" \

 				'Posix time zone string.'

 		done

 		TZ_for_date=$TZ;;

 	*)

 		# Get list of names of countries in the continent or ocean.

 		countries=$($AWK -F'\t' \

 			-v continent="$continent" \

 			-v TZ_COUNTRY_TABLE="$TZ_COUNTRY_TABLE" \

 		'

 			/^#/ { next }

 			$3 ~ ("^" continent "/") {

 				if (!cc_seen[$1]++) cc_list[++ccs] = $1

 			}

 			END {

 				while (getline <TZ_COUNTRY_TABLE) {

 					if ($0 !~ /^#/) cc_name[$1] = $2

 				}

 				for (i = 1; i <= ccs; i++) {

 					country = cc_list[i]

 					if (cc_name[country]) {

 					  country = cc_name[country]

 					}

 					print country

 				}

 			}

 		' <$TZ_ZONE_TABLE | sort -f)

 		# If there's more than one country, ask the user which one.

 		case $countries in

 		*"$newline"*)

 			echo >&2 'Please select a country.'

 			select country in $countries

 			do

 			    case $country in

 			    '') echo >&2 'Please enter a number in range.';;

 			    ?*) break

 			    esac

 			done

 			case $country in

 			'') exit 1

 			esac;;

 		*)

 			country=$countries

 		esac

 		# Get list of names of time zone rule regions in the country.

 		regions=$($AWK -F'\t' \

 			-v country="$country" \

 			-v TZ_COUNTRY_TABLE="$TZ_COUNTRY_TABLE" \

 		'

 			BEGIN {

 				cc = country

 				while (getline <TZ_COUNTRY_TABLE) {

 					if ($0 !~ /^#/  &&  country == $2) {

 						cc = $1

 						break

 					}

 				}

 			}

 			$1 == cc { print $4 }

 		' <$TZ_ZONE_TABLE)

 		# If there's more than one region, ask the user which one.

 		case $regions in

 		*"$newline"*)

 			echo >&2 'Please select one of the following' \

 				'time zone regions.'

 			select region in $regions

 			do

 				case $region in

 				'') echo >&2 'Please enter a number in range.';;

 				?*) break

 				esac

 			done

 			case $region in

 			'') exit 1

 			esac;;

 		*)

 			region=$regions

 		esac

 		# Determine TZ from country and region.

 		TZ=$($AWK -F'\t' \

 			-v country="$country" \

 			-v region="$region" \

 			-v TZ_COUNTRY_TABLE="$TZ_COUNTRY_TABLE" \

 		'

 			BEGIN {

 				cc = country

 				while (getline <TZ_COUNTRY_TABLE) {

 					if ($0 !~ /^#/  &&  country == $2) {

 						cc = $1

 						break

 					}

 				}

 			}

 			$1 == cc && $4 == region { print $3 }

 		' <$TZ_ZONE_TABLE)

 		# Make sure the corresponding zoneinfo file exists.

 		TZ_for_date=$TZDIR/$TZ

 		<$TZ_for_date || {

 			echo >&2 "$0: time zone files are not set up correctly"

 			exit 1

 		}

 	esac

 	# Use the proposed TZ to output the current date relative to UTC.

 	# Loop until they agree in seconds.

 	# Give up after 8 unsuccessful tries.

 	extra_info=

 	for i in 1 2 3 4 5 6 7 8

 	do

 		TZdate=$(LANG=C TZ="$TZ_for_date" date)

 		UTdate=$(LANG=C TZ=UTC0 date)

 		TZsec=$(expr "$TZdate" : '.*:\([0-5][0-9]\)')

 		UTsec=$(expr "$UTdate" : '.*:\([0-5][0-9]\)')

 		case $TZsec in

 		$UTsec)

 			extra_info="

 Local time is now:	$TZdate.

 Universal Time is now:	$UTdate."

 			break

 		esac

 	done

 	# Output TZ info and ask the user to confirm.

 	echo >&2 ""

 	echo >&2 "The following information has been given:"

 	echo >&2 ""

 	case $country+$region in

 	?*+?*)	echo >&2 "	$country$newline	$region";;

 	?*+)	echo >&2 "	$country";;

 	+)	echo >&2 "	TZ='$TZ'"

 	esac

 	echo >&2 ""

 	echo >&2 "Therefore TZ='$TZ' will be used.$extra_info"

 	echo >&2 "Is the above information OK?"

 	ok=

 	select ok in Yes No

 	do

 	    case $ok in

 	    '') echo >&2 'Please enter 1 for Yes, or 2 for No.';;

 	    ?*) break

 	    esac

 	done

 	case $ok in

 	'') exit 1;;

 	Yes) break

 	esac

 do :

 done

 case $SHELL in

 *csh) file=.login line="setenv TZ '$TZ'";;

 *) file=.profile line="TZ='$TZ'; export TZ"

 esac

 echo >&2 "

 You can make this change permanent for yourself by appending the line

 	$line

 to the file '$file' in your home directory; then log out and log in again.

 Here is that TZ value again, this time on standard output so that you

 can use the $0 command in shell scripts:"

 echo "$TZ"