How can I use the UNIX shell to count the number of times a letter appears in a text file?

Question

I have a few text files and I\'d like to count how many times a letter appears in each?

Specifically, I\'d like to use the UNIX shell to do this, in the form of: cat fil

Answer 1

echo "a/b/c/d/e/f/g" | awk -F"/" '{print NF}'

this will give the number of occurrence of character "/"