#### Listing 3. maildate.sh Script

#!/bin/bash
# maildate.sh - calculate date as integer days
# since 1900
# Sample input: "Feb 2 1997"
month=$1 # Received as three-character
# abbreviation
day=$2 # Received as integer 1 through 31
year=$3 # Received as integer 1900 through 2099
# Compute days from 1900 to beginning of year
# excluding leap days
days1900=$[ ( year - 1900 ) * 365 ]
# Compute approximate leap days since 1900 ; if
# current year is divisible by four and date is
# before 1 Mar then this will overstate leap
# days by one
leapdays=$[ ( year - 1900 ) / 4 ]
# If current year is a leap year then adjust if
# before 1 Mar
if [ $[ year % 4 ] -eq 0 ] && \
([ $month = "Jan" ] || [ $month = "Feb" ])
then
leapdays=$[ leapdays - 1]
fi<\n>
#Compute days into year
case $month in
'Jan') daysintoyear=0 ;;
'Feb') daysintoyear=31 ;;
'Mar') daysintoyear=59 ;;
'Apr') daysintoyear=90 ;;
'May') daysintoyear=120 ;;
'Jun') daysintoyear=151 ;;
'Jul') daysintoyear=181 ;;
'Aug') daysintoyear=212 ;;
'Sep') daysintoyear=243 ;;
'Oct') daysintoyear=273 ;;
'Nov') daysintoyear=304 ;;
'Dec') daysintoyear=334 ;;
esac
dayssince1900=$[ daysintoyear + leapdays + \
days1900 + day ]
echo $dayssince1900