Shell Script which reads a string and check whether it is palindrome or not

echo -e "Enter a string: \c"
read str
len=`expr length $str`
  
rev=""
while [ $len -gt 0 ]
do
    r=`echo $str | cut -c $len`
    rev=`echo $rev$r`
    len=`expr $len - 1`
done
echo Reverse of $str is $rev
if [ $str = $rev ]
then
    echo Palindrome
else
    echo Not palindrome
fi