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

As requested, a pure shell-script "solution":

sed -e "s/./\0\n/g" inputfile | sort -u

It's not nice, it's not fast and the output is not exactly as specified, but it should work ... mostly.

For even more ridiculousness, I present the version that dumps the output on one line:

sed -e "s/./\0\n/g" inputfile | sort -u | while read c; do echo -n "$c" ; done