Shell Programming and Scripting

#!/bin/ksh
gap=$1
start=0
limit=0
total=0
while read key min max amt
do
   if [ "$key" != "$ckey" ]
   then
       [ -n "$ckey" ] && echo $ckey $start $limit $total
       total=0
       start=$min
       let limit=start+gap
   fi
   if [ $limit -lt $min ]
   then
       echo $ckey $start $limit $total
           total=0
           start=$limit
           let limit+=gap
           while [ $start -le $(($min-$gap)) ]
           do
              echo $ckey $start $limit 0
              start=$limit
              let limit+=gap
           done
   fi
   ckey=$key
   let total+=amt
done < $2
echo $ckey $start $limit $total