Bash script to find the frequency of every letter in a file

Question

I am trying to find out the frequency of appearance of every letter in the english alphabet in an input file. How can I do this in a bash script?

Answer 1

A solution with sed, sort and uniq:

sed 's/\(.\)/\1\n/g' file | sort | uniq -c

This counts all characters, not only letters. You can filter out with:

sed 's/\(.\)/\1\n/g' file | grep '[A-Za-z]' | sort | uniq -c

If you want to consider uppercase and lowercase as same, just add a translation:

sed 's/\(.\)/\1\n/g' file | tr '[:upper:]' '[:lower:]' | grep '[a-z]' | sort | uniq -c