stupid, untested, probably with presentation errors solution to https://www.hackerrank.com/contests/pycode2015/challenges/dictionary-assignment

multi_sentence.sh

#!/bin/bash
 
split         () { grep -o .; }
remove_spaces () { grep -vP '[[:space:]]+'; }
count         () { sort | uniq -c; }
 
read -r _ # just ignore and halt on EoF
 
while read -r sentence
do
  echo "$sentence" | split | remove_spaces | count | while read -r count char
  do
    echo "Letter $char appears $count time/s"
  done
  echo
done

multi_sentence_test.sh

#!/bin/bash

bash tst.sh <<EoF 
100
asdsa
qwewq
o rato roeu a roupa do rei de roma
EoF

single_sentence.sh

#!/bin/bash

grep -o . | grep -vP '[[:space:]]+' | sort | uniq -c | while read -r count char
do
  echo "Letter $char appears $count time/s"
done