Check the string is palindrome or not |Shell Program|

#!/bin/bash
echo "Enter a string"
read str
len=`echo $str | wc -c`
len=`expr $len - 1`
b=`expr $len - 1`
i=1
j=`expr $len / 2`
while test $i -le $j
do
k=`echo $str |cut -c $i`
l=`echo $str |cut -c $len`
if test $k != $l
then
echo "$str is not a palindrome"
exit
fi
i=`expr $i + 1`
len=`expr $len - 1`
done
echo  "$str is a palindrome"

OUTPUT

Enter a string
malayalam
malayalam is a palindrome