#  cat lastday.ksh
#!/bin/ksh
cur_month=`date +%m`
cur_year=`date +%Y`
prev_month=$(($cur_month-1))

# Check to see if this is January
if [ $prev_month -lt 1 ]
then
prev_year=$(($cur_year-1))
prev_month=12
LastDayOfMonth=`/bin/cal $prev_month $cur_year | grep -v "^$" | sed -n  '1p;$p' | tr "\n" " "  | awk '{print substr($1,1,3),$NF,$2}'`
else
LastDayOfMonth=`/bin/cal $prev_month $cur_year | grep -v "^$" | sed -n  '1p;$p' | tr "\n" " "  | awk '{print substr($1,1,3),$NF,$2}'`
fi
echo $LastDayOfMonth


#  ./lastday.ksh
Jan 31 2008


#  date
Mon Feb 25 16:23:48 GMT 2008