Find Unique Characters in a File

Question

I have a file with 450,000+ rows of entries. Each entry is about 7 characters in length. What I want to know is the unique characters of this file.

For instance, if my f

Answer 1

cat yourfile | 
 perl -e 'while(<>){chomp;$k{$_}++ for split(//, lc $_)}print keys %k,"\n";'