timezone/tzselect.ksh

   1 #!/bin/bash
   2 # Ask the user about the time zone, and output the resulting TZ value to stdout.
   3 # Interact with the user via stderr and stdin.
   4
   5 PKGVERSION='(tzcode) '
   6 TZVERSION=see_Makefile
   7 REPORT_BUGS_TO=tz@iana.org
   8
   9 # Contributed by Paul Eggert.  This file is in the public domain.
  10
  11 # Porting notes:
  12 #
  13 # This script requires a POSIX-like shell and prefers the extension of a
  14 # 'select' statement.  The 'select' statement was introduced in the
  15 # Korn shell and is available in Bash and other shell implementations.
  16 # If your host lacks both Bash and the Korn shell, you can get their
  17 # source from one of these locations:
  18 #
  19 #       Bash <https://www.gnu.org/software/bash/>
  20 #       Korn Shell <http://www.kornshell.com/>
  21 #       MirBSD Korn Shell <http://www.mirbsd.org/mksh.htm>
  22 #
  23 # For portability to Solaris 10 /bin/sh (supported by Oracle through
  24 # January 2027) this script avoids some POSIX features and common
  25 # extensions, such as $(...), $((...)), ! CMD, unquoted ^, ${#ID},
  26 # ${ID##PAT}, ${ID%%PAT}, and $10.  Although some of these constructs
  27 # work sometimes, it's simpler to avoid them entirely.
  28 #
  29 # This script also uses several features of POSIX awk.
  30 # If your host lacks awk, or has an old awk that does not conform to POSIX,
  31 # you can use any of the following free programs instead:
  32 #
  33 #       Gawk (GNU awk) <https://www.gnu.org/software/gawk/>
  34 #       mawk <https://invisible-island.net/mawk/>
  35 #       nawk <https://github.com/onetrueawk/awk>
  36 #
  37 # Because 'awk "VAR=VALUE" ...' and 'awk -v "VAR=VALUE" ...' are not portable
  38 # if VALUE contains \, ", or newline, awk scripts in this file use:
  39 #   awk 'BEGIN { VAR = substr(ARGV[1], 2); ARGV[1] = "" } ...' ="VALUE"
  40 # The substr avoids problems when VALUE is of the form X=Y and would be
  41 # misinterpreted as an assignment.
  42
  43 # This script does not want path expansion.
  44 set -f
  45
  46 # Specify default values for environment variables if they are unset.
  47 : ${AWK=awk}
  48 : ${PWD=`pwd`}
  49 : ${TZDIR=$PWD}
  50
  51 # Output one argument as-is to standard output, with trailing newline.
  52 # Safer than 'echo', which can mishandle '\' or leading '-'.
  53 say() {
  54   printf '%s\n' "$1"
  55 }
  56
  57 # Check for awk POSIX compliance.
  58 ($AWK -v x=y 'BEGIN { exit 123 }') <>/dev/null >&0 2>&0
  59 [ $? = 123 ] || {
  60   say >&2 "$0: Sorry, your '$AWK' program is not POSIX compatible."
  61   exit 1
  62 }
  63
  64 coord=
  65 location_limit=10
  66 zonetabtype=zone1970
  67
  68 usage="Usage: tzselect [--version] [--help] [-c COORD] [-n LIMIT]
  69 Select a timezone interactively.
  70
  71 Options:
  72
  73   -c COORD
  74     Instead of asking for continent and then country and then city,
  75     ask for selection from time zones whose largest cities
  76     are closest to the location with geographical coordinates COORD.
  77     COORD should use ISO 6709 notation, for example, '-c +4852+00220'
  78     for Paris (in degrees and minutes, North and East), or
  79     '-c -35-058' for Buenos Aires (in degrees, South and West).
  80
  81   -n LIMIT
  82     Display at most LIMIT locations when -c is used (default $location_limit).
  83
  84   --version
  85     Output version information.
  86
  87   --help
  88     Output this help.
  89
  90 Report bugs to $REPORT_BUGS_TO."
  91
  92 # Ask the user to select from the function's arguments,
  93 # and assign the selected argument to the variable 'select_result'.
  94 # Exit on EOF or I/O error.  Use the shell's nicer 'select' builtin if
  95 # available, falling back on a portable substitute otherwise.
  96 if
  97   case $BASH_VERSION in
  98   ?*) :;;
  99   '')
 100     # '; exit' should be redundant, but Dash doesn't properly fail without it.
 101     (eval 'set --; select x; do break; done; exit') <>/dev/null 2>&0
 102   esac
 103 then
 104   # Do this inside 'eval', as otherwise the shell might exit when parsing it
 105   # even though it is never executed.
 106   eval '
 107     doselect() {
 108       select select_result
 109       do
 110         case $select_result in
 111         "") echo >&2 "Please enter a number in range.";;
 112         ?*) break
 113         esac
 114       done || exit
 115     }
 116   '
 117 else
 118   doselect() {
 119     # Field width of the prompt numbers.
 120     print_nargs_length="BEGIN {print length(\"$#\");}"
 121     select_width=`$AWK "$print_nargs_length"`
 122
 123     select_i=
 124
 125     while :
 126     do
 127       case $select_i in
 128       '')
 129         select_i=0
 130         for select_word
 131         do
 132           select_i=`$AWK "BEGIN { print $select_i + 1 }"`
 133           printf >&2 "%${select_width}d) %s\\n" $select_i "$select_word"
 134         done;;
 135       *[!0-9]*)
 136         echo >&2 'Please enter a number in range.';;
 137       *)
 138         if test 1 -le $select_i && test $select_i -le $#; then
 139           shift `$AWK "BEGIN { print $select_i - 1 }"`
 140           select_result=$1
 141           break
 142         fi
 143         echo >&2 'Please enter a number in range.'
 144       esac
 145
 146       # Prompt and read input.
 147       printf >&2 %s "${PS3-#? }"
 148       read select_i || exit
 149     done
 150   }
 151 fi
 152
 153 while getopts c:n:t:-: opt
 154 do
 155   case $opt$OPTARG in
 156   c*)
 157     coord=$OPTARG;;
 158   n*)
 159     location_limit=$OPTARG;;
 160   t*) # Undocumented option, used for developer testing.
 161     zonetabtype=$OPTARG;;
 162   -help)
 163     exec echo "$usage";;
 164   -version)
 165     exec echo "tzselect $PKGVERSION$TZVERSION";;
 166   -*)
 167     say >&2 "$0: -$opt$OPTARG: unknown option; try '$0 --help'"; exit 1;;
 168   *)
 169     say >&2 "$0: try '$0 --help'"; exit 1
 170   esac
 171 done
 172
 173 shift `$AWK "BEGIN { print $OPTIND - 1 }"`
 174 case $# in
 175 0) ;;
 176 *) say >&2 "$0: $1: unknown argument"; exit 1
 177 esac
 178
 179 # translit=true to try transliteration.
 180 # This is false if U+12345 CUNEIFORM SIGN URU TIMES KI has length 1
 181 # which means awk (and presumably the shell) do not need transliteration.
 182 if $AWK 'BEGIN { u12345 = "\360\222\215\205"; exit length(u12345) == 1 }'; then
 183   translit=true
 184 else
 185   translit=false
 186 fi
 187
 188 # Read into shell variable $1 the contents of file $2.
 189 # Convert to the current locale's encoding if possible,
 190 # as the shell aligns columns better that way.
 191 # If GNU iconv's //TRANSLIT does not work, fall back on POSIXish iconv;
 192 # if that does not work, fall back on 'cat'.
 193 read_file() {
 194   { $translit && {
 195     eval "$1=\`(iconv -f UTF-8 -t //TRANSLIT) 2>/dev/null <\"\$2\"\`" ||
 196     eval "$1=\`(iconv -f UTF-8) 2>/dev/null <\"\$2\"\`"
 197   }; } ||
 198   eval "$1=\`cat <\"\$2\"\`" || {
 199     say >&2 "$0: time zone files are not set up correctly"
 200     exit 1
 201   }
 202 }
 203 read_file TZ_COUNTRY_TABLE "$TZDIR/iso3166.tab"
 204 read_file TZ_ZONETABTYPE_TABLE "$TZDIR/$zonetabtype.tab"
 205 TZ_ZONENOW_TABLE=
 206
 207 newline='
 208 '
 209 IFS=$newline
 210
 211 # Awk script to output a country list.
 212 output_country_list='
 213   BEGIN {
 214     continent_re = substr(ARGV[1], 2)
 215     TZ_COUNTRY_TABLE = substr(ARGV[2], 2)
 216     TZ_ZONE_TABLE = substr(ARGV[3], 2)
 217     ARGV[1] = ARGV[2] = ARGV[3] = ""
 218     FS = "\t"
 219     nlines = split(TZ_ZONE_TABLE, line, /\n/)
 220     for (iline = 1; iline <= nlines; iline++) {
 221       $0 = line[iline]
 222       commentary = $0 ~ /^#@/
 223       if (commentary) {
 224         if ($0 !~ /^#@/)
 225           continue
 226         col1ccs = substr($1, 3)
 227         conts = $2
 228       } else {
 229         col1ccs = $1
 230         conts = $3
 231       }
 232       ncc = split(col1ccs, cc, /,/)
 233       ncont = split(conts, cont, /,/)
 234       for (i = 1; i <= ncc; i++) {
 235         elsewhere = commentary
 236         for (ci = 1; ci <= ncont; ci++) {
 237           if (cont[ci] ~ continent_re) {
 238             if (!cc_seen[cc[i]]++)
 239               cc_list[++ccs] = cc[i]
 240             elsewhere = 0
 241           }
 242         }
 243         if (elsewhere)
 244           for (i = 1; i <= ncc; i++)
 245             cc_elsewhere[cc[i]] = 1
 246       }
 247     }
 248     nlines = split(TZ_COUNTRY_TABLE, line, /\n/)
 249     for (i = 1; i <= nlines; i++) {
 250       $0 = line[i]
 251       if ($0 !~ /^#/)
 252         cc_name[$1] = $2
 253     }
 254     for (i = 1; i <= ccs; i++) {
 255       country = cc_list[i]
 256       if (cc_elsewhere[country])
 257         continue
 258       if (cc_name[country])
 259         country = cc_name[country]
 260       print country
 261     }
 262   }
 263 '
 264
 265 # Awk script to process a time zone table and output the same table,
 266 # with each row preceded by its distance from 'here'.
 267 # If output_times is set, each row is instead preceded by its local time
 268 # and any apostrophes are escaped for the shell.
 269 output_distances_or_times='
 270   BEGIN {
 271     coord = substr(ARGV[1], 2)
 272     TZ_COUNTRY_TABLE = substr(ARGV[2], 2)
 273     TZ_ZONE_TABLE = substr(ARGV[3], 2)
 274     ARGV[1] = ARGV[2] = ARGV[3] = ""
 275     FS = "\t"
 276     if (!output_times) {
 277       nlines = split(TZ_COUNTRY_TABLE, line, /\n/)
 278       for (i = 1; i <= nlines; i++) {
 279         $0 = line[i]
 280         if ($0 ~ /^#/)
 281           continue
 282         country[$1] = $2
 283       }
 284       country["US"] = "US" # Otherwise the strings get too long.
 285     }
 286   }
 287   function abs(x) {
 288     return x < 0 ? -x : x;
 289   }
 290   function min(x, y) {
 291     return x < y ? x : y;
 292   }
 293   function convert_coord(coord, deg, minute, ilen, sign, sec) {
 294     if (coord ~ /^[-+]?[0-9]?[0-9][0-9][0-9][0-9][0-9][0-9]([^0-9]|$)/) {
 295       degminsec = coord
 296       intdeg = degminsec < 0 ? -int(-degminsec / 10000) : int(degminsec / 10000)
 297       minsec = degminsec - intdeg * 10000
 298       intmin = minsec < 0 ? -int(-minsec / 100) : int(minsec / 100)
 299       sec = minsec - intmin * 100
 300       deg = (intdeg * 3600 + intmin * 60 + sec) / 3600
 301     } else if (coord ~ /^[-+]?[0-9]?[0-9][0-9][0-9][0-9]([^0-9]|$)/) {
 302       degmin = coord
 303       intdeg = degmin < 0 ? -int(-degmin / 100) : int(degmin / 100)
 304       minute = degmin - intdeg * 100
 305       deg = (intdeg * 60 + minute) / 60
 306     } else
 307       deg = coord
 308     return deg * 0.017453292519943296
 309   }
 310   function convert_latitude(coord) {
 311     match(coord, /..*[-+]/)
 312     return convert_coord(substr(coord, 1, RLENGTH - 1))
 313   }
 314   function convert_longitude(coord) {
 315     match(coord, /..*[-+]/)
 316     return convert_coord(substr(coord, RLENGTH))
 317   }
 318   # Great-circle distance between points with given latitude and longitude.
 319   # Inputs and output are in radians.  This uses the great-circle special
 320   # case of the Vicenty formula for distances on ellipsoids.
 321   function gcdist(lat1, long1, lat2, long2, dlong, x, y, num, denom) {
 322     dlong = long2 - long1
 323     x = cos(lat2) * sin(dlong)
 324     y = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(dlong)
 325     num = sqrt(x * x + y * y)
 326     denom = sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(dlong)
 327     return atan2(num, denom)
 328   }
 329   # Parallel distance between points with given latitude and longitude.
 330   # This is the product of the longitude difference and the cosine
 331   # of the latitude of the point that is further from the equator.
 332   # I.e., it considers longitudes to be further apart if they are
 333   # nearer the equator.
 334   function pardist(lat1, long1, lat2, long2) {
 335     return abs(long1 - long2) * min(cos(lat1), cos(lat2))
 336   }
 337   # The distance function is the sum of the great-circle distance and
 338   # the parallel distance.  It could be weighted.
 339   function dist(lat1, long1, lat2, long2) {
 340     return gcdist(lat1, long1, lat2, long2) + pardist(lat1, long1, lat2, long2)
 341   }
 342   BEGIN {
 343     coord_lat = convert_latitude(coord)
 344     coord_long = convert_longitude(coord)
 345     nlines = split(TZ_ZONE_TABLE, line, /\n/)
 346     for (h = 1; h <= nlines; h++) {
 347       $0 = line[h]
 348       if ($0 ~ /^#/)
 349         continue
 350       inline[inlines++] = $0
 351       ncc = split($1, cc, /,/)
 352       for (i = 1; i <= ncc; i++)
 353         cc_used[cc[i]]++
 354     }
 355     for (h = 0; h < inlines; h++) {
 356       $0 = inline[h]
 357       outline = $1 "\t" $2 "\t" $3
 358       sep = "\t"
 359       ncc = split($1, cc, /,/)
 360       split("", item_seen)
 361       item_seen[""] = 1
 362       for (i = 1; i <= ncc; i++) {
 363         item = cc_used[cc[i]] <= 1 ? country[cc[i]] : $4
 364         if (item_seen[item]++)
 365           continue
 366         outline = outline sep item
 367         sep = "; "
 368       }
 369       if (output_times) {
 370         fmt = "TZ='\''%s'\'' date +'\''%d %%Y %%m %%d %%H:%%M %%a %%b\t%s'\''\n"
 371         gsub(/'\''/, "&\\\\&&", outline)
 372         printf fmt, $3, h, outline
 373       } else {
 374         here_lat = convert_latitude($2)
 375         here_long = convert_longitude($2)
 376         printf "%g\t%s\n", dist(coord_lat, coord_long, here_lat, here_long), \
 377           outline
 378       }
 379     }
 380   }
 381 '
 382
 383 # Begin the main loop.  We come back here if the user wants to retry.
 384 while
 385
 386   echo >&2 'Please identify a location' \
 387     'so that time zone rules can be set correctly.'
 388
 389   continent=
 390   country=
 391   country_result=
 392   region=
 393   time=
 394   TZ_ZONE_TABLE=$TZ_ZONETABTYPE_TABLE
 395
 396   case $coord in
 397   ?*)
 398     continent=coord;;
 399   '')
 400
 401     # Ask the user for continent or ocean.
 402
 403     echo >&2 \
 404       'Please select a continent, ocean, "coord", "TZ", "time", or "now".'
 405
 406     quoted_continents=`
 407       $AWK '
 408         function handle_entry(entry) {
 409           entry = substr(entry, 1, index(entry, "/") - 1)
 410           if (entry == "America")
 411             entry = entry "s"
 412           if (entry ~ /^(Arctic|Atlantic|Indian|Pacific)$/)
 413             entry = entry " Ocean"
 414           printf "'\''%s'\''\n", entry
 415         }
 416         BEGIN {
 417           TZ_ZONETABTYPE_TABLE = substr(ARGV[1], 2)
 418           ARGV[1] = ""
 419           FS = "\t"
 420           nlines = split(TZ_ZONETABTYPE_TABLE, line, /\n/)
 421           for (i = 1; i <= nlines; i++) {
 422             $0 = line[i]
 423             if ($0 ~ /^[^#]/)
 424               handle_entry($3)
 425             else if ($0 ~ /^#@/) {
 426               ncont = split($2, cont, /,/)
 427               for (ci = 1; ci <= ncont; ci++)
 428                 handle_entry(cont[ci])
 429             }
 430           }
 431         }
 432       ' ="$TZ_ZONETABTYPE_TABLE" |
 433       sort -u |
 434       tr '\n' ' '
 435       echo ''
 436     `
 437
 438     eval '
 439       doselect '"$quoted_continents"' \
 440         "coord - I want to use geographical coordinates." \
 441         "TZ - I want to specify the timezone using a POSIX.1-2017 TZ string." \
 442         "time - I know local time already." \
 443         "now - Like \"time\", but configure only for timestamps from now on."
 444       continent=$select_result
 445       case $continent in
 446       Americas) continent=America;;
 447       *)
 448         # Get the first word of $continent.  Path expansion is disabled
 449         # so this works even with "*", which should not happen.
 450         IFS=" "
 451         for continent in $continent ""; do break; done
 452         IFS=$newline;;
 453       esac
 454       case $zonetabtype,$continent in
 455       zonenow,*) ;;
 456       *,now)
 457         ${TZ_ZONENOW_TABLE:+:} read_file TZ_ZONENOW_TABLE "$TZDIR/zonenow.tab"
 458         TZ_ZONE_TABLE=$TZ_ZONENOW_TABLE
 459       esac
 460     '
 461   esac
 462
 463   case $continent in
 464   TZ)
 465     # Ask the user for a POSIX.1-2017 TZ string.  Check that it conforms.
 466     check_POSIX_TZ_string='
 467       BEGIN {
 468         tz = substr(ARGV[1], 2)
 469         ARGV[1] = ""
 470         tzname = ("(<[[:alnum:]+-][[:alnum:]+-][[:alnum:]+-]+>" \
 471                   "|[[:alpha:]][[:alpha:]][[:alpha:]]+)")
 472         time = ("(2[0-4]|[0-1]?[0-9])" \
 473                 "(:[0-5][0-9](:[0-5][0-9])?)?")
 474         offset = "[-+]?" time
 475         mdate = "M([1-9]|1[0-2])\\.[1-5]\\.[0-6]"
 476         jdate = ("((J[1-9]|[0-9]|J?[1-9][0-9]" \
 477                  "|J?[1-2][0-9][0-9])|J?3[0-5][0-9]|J?36[0-5])")
 478         datetime = ",(" mdate "|" jdate ")(/" time ")?"
 479         tzpattern = ("^(:.*|" tzname offset "(" tzname \
 480                      "(" offset ")?(" datetime datetime ")?)?)$")
 481         exit tz ~ tzpattern
 482       }
 483     '
 484
 485     while
 486       echo >&2 'Please enter the desired value' \
 487         'of the TZ environment variable.'
 488       echo >&2 'For example, AEST-10 is abbreviated' \
 489         'AEST and is 10 hours'
 490       echo >&2 'ahead (east) of Greenwich,' \
 491         'with no daylight saving time.'
 492       read tz
 493       $AWK "$check_POSIX_TZ_string" ="$tz"
 494     do
 495       say >&2 "'$tz' is not a conforming POSIX.1-2017 timezone string."
 496     done
 497     TZ_for_date=$tz;;
 498   *)
 499     case $continent in
 500     coord)
 501       case $coord in
 502       '')
 503         echo >&2 'Please enter coordinates' \
 504           'in ISO 6709 notation.'
 505         echo >&2 'For example, +4042-07403 stands for'
 506         echo >&2 '40 degrees 42 minutes north,' \
 507           '74 degrees 3 minutes west.'
 508         read coord
 509       esac
 510       distance_table=`
 511         $AWK \
 512           "$output_distances_or_times" \
 513           ="$coord" ="$TZ_COUNTRY_TABLE" ="$TZ_ZONE_TABLE" |
 514         sort -n |
 515         $AWK "{print} NR == $location_limit { exit }"
 516       `
 517       regions=`
 518         $AWK '
 519           BEGIN {
 520             distance_table = substr(ARGV[1], 2)
 521             ARGV[1] = ""
 522             nlines = split(distance_table, line, /\n/)
 523             for (nr = 1; nr <= nlines; nr++) {
 524               nf = split(line[nr], f, /\t/)
 525               print f[nf]
 526             }
 527           }
 528         ' ="$distance_table"
 529       `
 530       echo >&2 'Please select one of the following timezones,'
 531       echo >&2 'listed roughly in increasing order' \
 532         "of distance from $coord".
 533       doselect $regions
 534       region=$select_result
 535       tz=`
 536         $AWK '
 537           BEGIN {
 538             distance_table = substr(ARGV[1], 2)
 539             region = substr(ARGV[2], 2)
 540             ARGV[1] = ARGV[2] = ""
 541             nlines = split(distance_table, line, /\n/)
 542             for (nr = 1; nr <= nlines; nr++) {
 543               nf = split(line[nr], f, /\t/)
 544               if (f[nf] == region)
 545                 print f[4]
 546             }
 547           }
 548         ' ="$distance_table" ="$region"
 549       `;;
 550     *)
 551       case $continent in
 552       now|time)
 553         minute_format='%a %b %d %H:%M'
 554         old_minute=`TZ=UTC0 date +"$minute_format"`
 555         for i in 1 2 3
 556         do
 557           time_table_command=`
 558             $AWK \
 559               -v output_times=1 \
 560               "$output_distances_or_times" \
 561               = = ="$TZ_ZONE_TABLE"
 562           `
 563           time_table=`eval "$time_table_command"`
 564           new_minute=`TZ=UTC0 date +"$minute_format"`
 565           case $old_minute in
 566           "$new_minute") break
 567           esac
 568           old_minute=$new_minute
 569         done
 570         echo >&2 "The system says Universal Time is $new_minute."
 571         echo >&2 "Assuming that's correct, what is the local time?"
 572         sorted_table=`say "$time_table" | sort -k2n -k2,5 -k1n` || {
 573           say >&2 "$0: cannot sort time table"
 574           exit 1
 575         }
 576         eval doselect `
 577           $AWK '
 578             BEGIN {
 579               sorted_table = substr(ARGV[1], 2)
 580               ARGV[1] = ""
 581               nlines = split(sorted_table, line, /\n/)
 582               for (i = 1; i <= nlines; i++) {
 583                 $0 = line[i]
 584                 outline = $6 " " $7 " " $4 " " $5
 585                 if (outline == oldline)
 586                   continue
 587                 oldline = outline
 588                 gsub(/'\''/, "&\\\\&&", outline)
 589                 printf "'\''%s'\''\n", outline
 590               }
 591             }
 592           ' ="$sorted_table"
 593         `
 594         time=$select_result
 595         continent_re='^'
 596         zone_table=`
 597           $AWK '
 598             BEGIN {
 599               time = substr(ARGV[1], 2)
 600               time_table = substr(ARGV[2], 2)
 601               ARGV[1] = ARGV[2] = ""
 602               nlines = split(time_table, line, /\n/)
 603               for (i = 1; i <= nlines; i++) {
 604                 $0 = line[i]
 605                 if ($6 " " $7 " " $4 " " $5 == time) {
 606                   sub(/[^\t]*\t/, "")
 607                   print
 608                 }
 609               }
 610             }
 611           ' ="$time" ="$time_table"
 612         `
 613         countries=`
 614           $AWK \
 615             "$output_country_list" \
 616             ="$continent_re" ="$TZ_COUNTRY_TABLE" ="$zone_table" |
 617           sort -f
 618         `
 619         ;;
 620       *)
 621         continent_re="^$continent/"
 622         zone_table=$TZ_ZONE_TABLE
 623       esac
 624
 625       # Get list of names of countries in the continent or ocean.
 626       countries=`
 627         $AWK \
 628           "$output_country_list" \
 629           ="$continent_re" ="$TZ_COUNTRY_TABLE" ="$zone_table" |
 630         sort -f
 631       `
 632       # If all zone table entries have comments, and there are
 633       # at most 22 entries, asked based on those comments.
 634       # This fits the prompt onto old-fashioned 24-line screens.
 635       regions=`
 636         $AWK '
 637           BEGIN {
 638             TZ_ZONE_TABLE = substr(ARGV[1], 2)
 639             ARGV[1] = ""
 640             FS = "\t"
 641             nlines = split(TZ_ZONE_TABLE, line, /\n/)
 642             for (i = 1; i <= nlines; i++) {
 643               $0 = line[i]
 644               if ($0 ~ /^[^#]/ && !missing_comment) {
 645                 if ($4)
 646                   comment[++inlines] = $4
 647                 else
 648                   missing_comment = 1
 649               }
 650             }
 651             if (!missing_comment && inlines <= 22)
 652               for (i = 1; i <= inlines; i++)
 653                 print comment[i]
 654           }
 655         ' ="$zone_table"
 656       `
 657
 658       # If there's more than one country, ask the user which one.
 659       case $countries in
 660       *"$newline"*)
 661         echo >&2 'Please select a country' \
 662           'whose clocks agree with yours.'
 663         doselect $countries
 664         country_result=$select_result
 665         country=$select_result;;
 666       *)
 667         country=$countries
 668       esac
 669
 670
 671       # Get list of timezones in the country.
 672       regions=`
 673         $AWK '
 674           BEGIN {
 675             country = substr(ARGV[1], 2)
 676             TZ_COUNTRY_TABLE = substr(ARGV[2], 2)
 677             TZ_ZONE_TABLE = substr(ARGV[3], 2)
 678             ARGV[1] = ARGV[2] = ARGV[3] = ""
 679             FS = "\t"
 680             cc = country
 681             nlines = split(TZ_COUNTRY_TABLE, line, /\n/)
 682             for (i = 1; i <= nlines; i++) {
 683               $0 = line[i]
 684               if ($0 !~ /^#/  &&  country == $2) {
 685                 cc = $1
 686                 break
 687               }
 688             }
 689             nlines = split(TZ_ZONE_TABLE, line, /\n/)
 690             for (i = 1; i <= nlines; i++) {
 691               $0 = line[i]
 692               if ($0 ~ /^#/)
 693                 continue
 694               if ($1 ~ cc)
 695                 print $4
 696             }
 697           }
 698         ' ="$country" ="$TZ_COUNTRY_TABLE" ="$zone_table"
 699       `
 700
 701       # If there's more than one region, ask the user which one.
 702       case $regions in
 703       *"$newline"*)
 704         echo >&2 'Please select one of the following timezones.'
 705         doselect $regions
 706         region=$select_result
 707       esac
 708
 709       # Determine tz from country and region.
 710       tz=`
 711         $AWK '
 712           BEGIN {
 713             country = substr(ARGV[1], 2)
 714             region = substr(ARGV[2], 2)
 715             TZ_COUNTRY_TABLE = substr(ARGV[3], 2)
 716             TZ_ZONE_TABLE = substr(ARGV[4], 2)
 717             ARGV[1] = ARGV[2] = ARGV[3] = ARGV[4] = ""
 718             FS = "\t"
 719             cc = country
 720             nlines = split(TZ_COUNTRY_TABLE, line, /\n/)
 721             for (i = 1; i <= nlines; i++) {
 722               $0 = line[i]
 723               if ($0 !~ /^#/  &&  country == $2) {
 724                 cc = $1
 725                 break
 726               }
 727             }
 728             nlines = split(TZ_ZONE_TABLE, line, /\n/)
 729             for (i = 1; i <= nlines; i++) {
 730               $0 = line[i]
 731               if ($0 ~ /^#/)
 732                 continue
 733               if ($1 ~ cc && ($4 == region || !region))
 734                 print $3
 735             }
 736           }
 737         ' ="$country" ="$region" ="$TZ_COUNTRY_TABLE" ="$zone_table"
 738       `
 739     esac
 740
 741     # Make sure the corresponding zoneinfo file exists.
 742     TZ_for_date=$TZDIR/$tz
 743     <"$TZ_for_date" || {
 744       say >&2 "$0: time zone files are not set up correctly"
 745       exit 1
 746     }
 747   esac
 748
 749
 750   # Use the proposed TZ to output the current date relative to UTC.
 751   # Loop until they agree in seconds.
 752   # Give up after 8 unsuccessful tries.
 753
 754   extra_info=
 755   for i in 1 2 3 4 5 6 7 8
 756   do
 757     TZdate=`LANG=C TZ="$TZ_for_date" date`
 758     UTdate=`LANG=C TZ=UTC0 date`
 759     if $AWK '
 760           function getsecs(d) {
 761             return match(d, /.*:[0-5][0-9]/) ? substr(d, RLENGTH - 1, 2) : ""
 762           }
 763           BEGIN { exit getsecs(ARGV[1]) != getsecs(ARGV[2]) }
 764        ' ="$TZdate" ="$UTdate"
 765     then
 766       extra_info="
 767 Selected time is now:   $TZdate.
 768 Universal Time is now:  $UTdate."
 769       break
 770     fi
 771   done
 772
 773
 774   # Output TZ info and ask the user to confirm.
 775
 776   echo >&2 ""
 777   echo >&2 "Based on the following information:"
 778   echo >&2 ""
 779   case $time%$country_result%$region%$coord in
 780   ?*%?*%?*%)
 781     say >&2 "   $time$newline   $country_result$newline $region";;
 782   ?*%?*%%|?*%%?*%) say >&2 "    $time$newline   $country_result$region";;
 783   ?*%%%)        say >&2 "       $time";;
 784   %?*%?*%)      say >&2 "       $country_result$newline $region";;
 785   %?*%%)        say >&2 "       $country_result";;
 786   %%?*%?*)      say >&2 "       coord $coord$newline    $region";;
 787   %%%?*)        say >&2 "       coord $coord";;
 788   *)            say >&2 "       TZ='$tz'"
 789   esac
 790   say >&2 ""
 791   say >&2 "TZ='$tz' will be used.$extra_info"
 792   say >&2 "Is the above information OK?"
 793
 794   doselect Yes No
 795   ok=$select_result
 796   case $ok in
 797   Yes) break
 798   esac
 799 do coord=
 800 done
 801
 802 case $SHELL in
 803 *csh) file=.login line="setenv TZ '$tz'";;
 804 *)    file=.profile line="TZ='$tz'; export TZ"
 805 esac
 806
 807 test -t 1 && say >&2 "
 808 You can make this change permanent for yourself by appending the line
 809         $line
 810 to the file '$file' in your home directory; then log out and log in again.
 811
 812 Here is that TZ value again, this time on standard output so that you
 813 can use the $0 command in shell scripts:"
 814
 815 say "$tz"