Shell Script to find Vowels and Consonants

echo "Enter String"
read s
c=`echo $s|cat >> tmp`
count=0
cons=0
a=1
wc=`cat tmp|wc -m`
while test $a -lt $wc
do
r=`cut -c $a tmp`
case $r in
a)
count=`expr $count + 1`
;;
e)
count=`expr $count + 1`
;;
i)
count=`expr $count + 1`
;;
o)
count=`expr $count + 1`
;;
u)
count=`expr $count + 1`
;;
*)
cons=`expr $cons + 1`
esac
a=`expr $a + 1`
done
echo "$count Vowels"
echo "$cons consonants "
x=`rm tmp`