UNIX for Advanced & Expert Users

#!/bin/ksh 

set -A mycount  0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
set -A alphabet A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
let offset=0
char=""
record=""
add_letter ()
{
   let offset=30
   case $char in
     [Aa]) let offset=1
     ;;
     [Bb]) let offset=2
     ;;
     [Cc]) let offset=3
     ;;
     [Dd]) let offset=4
     ;;
     [Ee]) let offset=5
     ;;
     [Ff]) let offset=6
     ;;
     [Gg]) let offset=7
     ;;
     [Hh]) let offset=8
     ;;
     [Ii]) let offset=9
     ;;
     [Jj]) let offset=10
     ;;
     [Kk]) let offset=11
     ;;
     [Ll]) let offset=12
     ;;
     [Mm]) let offset=13
     ;;
     [Nn]) let offset=14
     ;;
     [Oo]) let offset=15
     ;;
     [Pp]) let offset=16
     ;;
     [Qq]) let offset=17
     ;;
     [Rr]) let offset=18
     ;;
     [Ss]) let offset=19
     ;;     
     [Tt]) let offset=20
     ;;
     [Uu]) let offset=21
     ;;
     [Vv]) let offset=22
     ;;
     [Ww]) let offset=23
     ;;
     [Xx]) let offset=24
     ;;
     [Yy]) let offset=25
     ;;
     [Zz]) let offset=26
     ;;
    esac 
    if [ $offset -lt 30 ]; then
       let offset=$offset-1
       mycount[$offset]=`echo "${mycount[offset]} + 1" | bc`
    fi
}
split_to_char()
{
	echo $record | awk '{ for (i=1;i<length($0);i++) print substr($0,i,1) }' |
	while read char
	do
	   
	    add_letter
    done
}

while read record
do
   split_to_char;    
done < $1

touch tmp.tmp

> tmp.tmp

let i=0

while [ $i -lt ${#mycount[*]} ]
do
     printf "%5d %s\n" ${mycount[i]} ${alphabet[i]} >> tmp.tmp
     let i=$i+1
done
echo "Letter count for $1"
echo "Count Letter"
echo "----- ------"
sort -n tmp.tmp 
echo " "
echo "Most common letter"
echo "Count Letter"
echo "----- ------"
sort -n -r tmp.tmp  | head -1
rm -f tmp.tmp
exit