#!/bin/bash

line=$(head -n 1 "$1")
size=${#line}
for i in $(seq 1 $(($size)))
do
  awk '{print substr($0,'$i',1)}' "$1" | tr -d '\n' | tr -s ' ' | tr ' ' '\n' | sort | uniq | sed -r '/^.{,2}$/d'
done

cat "$1" | tr ' ' '\n' | sort | uniq | sed -r '/^.{,2}$/d'