Program to print 1089 numbers from 100 to 1000 in Linux/Unix

i=100
while [ $i -le 999 ]
do
n=$i
num=$n
s=0
r=0
while [ $n != 0 ]
do
r=` expr $n \% 10 `
s=` expr $s \* 10 \+ $r `
n=` expr $n \/ 10 `
done



if [ $s -gt $num ]
then
s=` expr $s \- $num `
else
s=` expr $num \- $s `
fi


n=$s
nu=$n
s=0
r=0
while [ $n != 0 ]
do
r=` expr $n \% 10 `
s=` expr $s \* 10 \+ $r `
n=` expr $n \/ 10 `
done
if [ $s -lt 100 ]
then
s=` expr $s \* 10 `
fi

s=` expr $s \+ $nu `

if [ $s -eq 1089 ]
then
echo  $i
fi
i=` expr $i \+ 1 `
done