#!/bin/sh
# valid-date -- Validates a date, taking into account leap year rules.
exceedsDaysInMonth()
{
case $(echo $1|tr '[:upper:]' '[:lower:]') in
jan* ) days=31 ;; feb* ) days=28 ;;
mar* ) days=31 ;; apr* ) days=30 ;;
may* ) days=31 ;; jun* ) days=30 ;;
jul* ) days=31 ;; aug* ) days=31 ;;
sep* ) days=30 ;; oct* ) days=31 ;;
nov* ) days=30 ;; dec* ) days=31 ;;
* ) echo "$0: Unknown month name $1" >2; exit 1
esac
if [ $2 -lt 1 -o $2 -gt $days ] ; then
return 1
else
return 0 # the day number is valid
fi
}
isLeapYear()
{
year=$1
if [ "$((year % 4))" -ne 0 ] ; then
return 1 # nope, not a leap year
elif [ "$((year % 400))" -eq 0 ] ; then
return 0 # yes, it's a leap year
elif [ "$((year % 100))" -eq 0 ] ; then
return 1
else
return 0
fi
}
## Begin main script
if [ $# -ne 3 ] ; then
echo "Usage: $0 month day year" >2
echo "Typical input formats are 8 3 2002" >2
exit 1
fi
# Normalize date and split back out returned values
if [ $? -eq 1 ] ; then
exit 1 # error condition already reported by normdate
fi
monthnoToName()
{
# Sets the variable 'month' to the appropriate value
case $1 in
01|1 ) monthd="Jan" ;; 02|2 ) monthd="Feb" ;;
03|3 ) monthd="Mar" ;; 04|4 ) monthd="Apr" ;;
05|5 ) monthd="May" ;; 06|6 ) monthd="Jun" ;;
07|7 ) monthd="Jul" ;; 08|8 ) monthd="Aug" ;;
09|9 ) monthd="Sep" ;; 10) monthd="Oct" ;;
11) monthd="Nov" ;; 12) monthd="Dec" ;;
* ) echo "$0: Unknown numeric month value $1" >2; exit 1
esac
return 0
}
monthnoToName $1
month="$monthd"
day="$2"
year="$3"
if ! exceedsDaysInMonth $month "$2" ; then
if [ "$month" = "Feb" -a "$2" -eq "29" ] ; then
if ! isLeapYear $3 ; then
echo "$0: $3 is not a leap year, so Feb doesn't have 29 days" >2
exit 1
fi
else
echo "$0: bad day value: $month doesn't have $2 days" >2
exit 1
fi
fi
echo "Valid date: $newdate"
exit 0
