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

awk '{ printf "%s\n", gsub( "ur_char", "oth_char", $0 ) }' < your_file_name > output.txt

you can add count of current line number to get the line numbers in awk also.