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

Here is another way

cat  input_file | \
awk 'BEGIN {FS="x"; var=0 } \
{if (NF>0){ var=var + (NF-1) } } \
END{print var}'

where X is the character or string of characters you want to count and infile is the input file