Shell Programming and Scripting

#!/bin/ksh
# usage: vdate.shl <date> where date = month/day/year
# valid for date = or > 10/04/1582 -- start of Gregorian calendar

isleapyr()
{
	isleap=0
	if [[ $(( ${1} % 400 )) -eq 0  ||
	      $(( ${1} % 4 )) -eq 0 && $(( ${1} % 100 )) -ne 0 ]]
	then
	   isleap=1
	fi
}

isvaliddate()
{
 	typeset -i day=$1
 	typeset -i month=$2
 	typeset -i year=$3
	set -A arr 31 28 31 30 31 30 31 31 30 31 30 31
	
 	if [[ $year -lt 34 ]] ; then  # assume 2000 
 		year=$(( $year + 2000 ))
 	fi
 	if [[ $year -gt 33 && $year -lt 100 ]] ; then  # assume 1900
 	    year=$(( $year + 1900 ))
 	fi
 	
 	isleapyr $year
    if [[ $isleap -eq 1 ]] ; then
    	arr[1]=29;
    fi
 
 	if [[ $month -gt 0 && $month -lt 13 ]] ; then
 		month=$(( $month - 1 ))
 		if [[ $day -gt 0 && $day -le ${arr[month]} ]] ; then
 			return 0
 		fi
 	fi
 	return 1
}

echo "$1" | tr -s '/' ' ' | read month day year
isvaliddate $day $month $year

if [[ $? -eq 0 ]] ; then
  echo "$1 ok"
else
  echo "$1 not ok"
fi

IFS="/"
set $1
if [ $1 -lt 0 ] || [ $1 -gt 12 ];then
	echo "Error month"
elif [ $2 -lt 0 ] || [ $2 -gt 31 ];then
	echo "Error day"
else
	echo "hello $*"
fi