#!/bin/sh

usage() {
	echo "usage: $0 <file> <letter1> [letter2] [letter3] [...]"
	exit 1
}

[[ ! -f "$1" ]] && echo "file does not exist" && usage
[[ "$#" -lt 2 ]] && echo "not enough arguments" && usage

file="$1"
shift
for letter in "$@"; do
	[[ ! "${#letter}" -eq 1 ]] && echo "argument \"$letter\" too long" && usage
	echo "$letter -> `cat $file | tr -cd $letter | wc -c`"
done