Re: Guessing the date style from the timezone for postgresql postinst

["Oliver Elphick" <olly@lfix.co.uk>]

Carey Evans wrote:
  >"Oliver Elphick" <olly@lfix.co.uk> writes:
  >
  >> If you have a recent potato system, with timezone files in
  >> /usr/share/zoneinfo, could you please run the script and let me know if
  >> it gives WRONG results for you.  If it does, please tell me your timezone
  >> and offset (date '+%Z %z') and what the date style ought to be. If you
  >> can suggest a change to the script that will get it right without breaking
      > 
  >> results for other countries, that will be even better!
  >
  >Given my normal environment, the script doesn't work out which country 
  >I'm in:
  >
 
Here's a revised version of the script taking into account all comments
so far.

Raul Miller wrote:
  >On Fri, Sep 17, 1999 at 11:20:13PM -0400, Joe Drew wrote:
  >> It's my personal preference that ISO standard be used unless otherwise
  >> told - but that's me.
  >
  >I tend to agree.  It would just be so simple to have the default be ISO.
  >
  >As ISO is very unambiguous, I don't think it would cause problems, either.
  >Then again, maybe someone else knows of problems it would create...

I agree that it would make things simpler, but I doubt that most people
would actually prefer it, because it isn't the way we naturally think of
dates.

Joe Drew wrote:
  >Canada is a very multicultural country, and it really is every
  >person for him- or herself.

That being so, it definitely makes sense to use ISO for Canada.

Of course, the installer can override the guess, but I like to guess as
close as possible.


#! /bin/sh
# Guess the postgresql datestyle to use for a given timezone (from glibc)

# make sure we can find the timezone database
ZONEDIR=`ls -l /etc/localtime | awk '{print $NF}' | cut -d/ -f1-4`
if [ ! -d "$ZONEDIR" ]
then
	echo "Sorry, I don't know where to find the timezone files; this
script expected to find them in $ZONEDIR"
	exit 1
fi

# make sure TZ is set and exported
if [ -z "$TZ" ]
then
	TZ=`ls -l /etc/localtime | awk '{print $NF}' | cut -d/ -f5-10`
fi
export TZ

# find the timezone offset from UTC
tzno=`date '+%z'`

# Find the name of the zone - strip off unwanted header directories
x=`echo $TZ | cut -d/ -f1`
case $x in ( SystemV | posix | right )
	x=`echo $TZ | cut -d/ -f2-4`
	;;
	* )
		x=$TZ
		;;
esac

# What country does this zone belong to (if undefined, set it to __)
tzcountry=`grep $x $ZONEDIR/zone.tab | head -1 | cut -c1-2` 
if [ -z "$tzcountry" ]
then
	tzcountry=__
fi

# Guess the timezone
case $tzcountry in ( US )
		# US date format
		GuessDateStyle=US
		;;
	AR )
		# Argentina
		GuessDateStyle=SQL
		;;
	CA )
		# Canada has no standard
		GuessDateStyle=ISO
		;;
	DE )
		# Germany has a style to itself
		GuessDateStyle=GERMAN
		;;
	__ )
		# No country, so see if the zone is a region or country name
		x=$TZ
		while echo $x | grep -q /
		do
			y=`dirname $x`
			case $y in ( SystemV | posix | right )
				y=`basename $x`
				;;
			esac
			x=$y
		done

		case $x in ( Africa | Canada | Indian | Mexico | America | Chile | GB | Iran | Mideast | Antarctica | Cuba | Israel | NZ | Singapore | Arctic | Jamaica | Asia | Japan | Navajo | Turkey | Atlantic | Kwajalein | Australia | Egypt | Libya | US | Brazil | Eire | Pacific | Hongkong | Poland | Europe | Iceland | Portugal)
			# try to guess the zone from the UTC offset and the
			# zone abbreviation
			if [ -z "$GuessDateStyle" ]
			then
				GuessDateStyle=EURO
				if [ "$LANG" = de_DE ]
				then
					GuessDateStyle=GERMAN
				elif [ $tzno -le -200 -a $tzno -gt -1200 ]
				then
					tzn=`date '+%Z'`
					case $tzn in ( ADT | AST | AKDT | AKST | CDT | CST | EDT | EST | HADT | HAST | HST | MDT | MST | NDT | PDT | PST)
						GuessDateStyle=US
						;;
					esac
				fi
			fi
			;;
		* )
			# Not a country or region so use ISO
			GuessDateStyle=ISO
			;;
		esac
		;;
	* )
		# The rest of the world uses normal European format
		GuessDateStyle=EURO
		;;
esac
echo $tzcountry $GuessDateStyle

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Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
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