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I would like to find out the number of occurrences of each of the alphabets in a word. Eg

aabbbddd 

a@2 b@3 c@0 d@3

How can I perform this using shell script?

These solutions are case-insensitive:

start cmd:> echo aabbbddd | 

  awk -v FS= '{for (i=1;i<=NF;i++) a[tolower($i)]++;}; 

    END {for (key in a) print key ": " a[key];}'

a: 2

b: 3

d: 3

Or for the complete alphabet:

start cmd:> echo Aabbbddd | 

  awk -v FS= '{for (i=1;i<=NF;i++) a[tolower($i)]++;};

    END {chars="abcdefghijklmnopqrstuvwxyz";

    for (i=1;i<27;i++) { key=substr(chars,i,1);print key ": " a[key]};}'

a: 2

b: 3

c: 

d: 3

e: 

f: 

g: 

h: 

i: 

j: 

k: 

l: 

m: 

n: 

o: 

p: 

q: 

r: 

s: 

t: 

u: 

v: 

w: 

x: 

y: 

z:

You could use sed, uniq, and sort:

$ echo -n "aabbbddd" | sed 's/(.)/1n/g'| sort | uniq -c

  2 a

  3 b

  3 d

The above uses sed to take each character and replace it with itself + a newline (n). Now with each character on a newline (and sorted) you can use uniq -c to count the characters.

NOTE: This method will not show any of the characters in between that have zero occurrences.

Alternatively showing each letter's count

$ s="aabbbddd"; for i in {a..z}; do

     v=$(echo -n "$s" | grep -oi $i | wc -l); echo "$i : $v"; done

a : 2

b : 3

c : 0

d : 3

e : 0

f : 0

g : 0

h : 0

i : 0

j : 0

k : 0

l : 0

m : 0

n : 0

o : 0

p : 0

q : 0

r : 0

s : 0

t : 0

u : 0

v : 0

w : 0

x : 0

y : 0

z : 0

This works by looping through all the letters of the alphabet:

 for i in {a..z}; do .... ; done

Each iteration of the loop we grep through the string looking for a specific character, and use the -o option of grep to only return these matches. We then use wc -l to count how many occurrences of each letter we found, and store it in variable $v. We then display each iteration:

 echo "$i : $v"

NOTE: This approach can handle the strings being out of order.

Using only the shell (faster for short strings):

#! /bin/bash -

input=${*:-'aabbbddd'}



tmp=$input

arr=()

maxlen=0

maxchar=''

while ((${#tmp})); do

    firstchar=${tmp:0:1}

    next=${tmp//"$firstchar"}

    len=$((${#tmp}-${#next}))

    arr+=("$firstchar: $len")

    if ((maxlen<len)); then

    maxlen=$len

    maxchar=$firstchar

    fi

    tmp=$next

done



printf '%sn' "${arr[@]}" 

echo "The char "$maxchar" appear $maxlen times in "$input""

Called as:

$ ./script

a@2 b@3 d@3 

The char "b" appear 3 times in "aabbbddd"