extracting unique values between 2 sets/files

Question

Working in linux/shell env, how can I accomplish the following:

text file 1 contains:

1
2
3
4
5

text file 2 contains:

Answer 1

How about:

diff file_1 file_2 | grep '^>' | cut -c 3-

This would print the entries in file_2 which are not in file_1. For the opposite result one just has to replace '>' with '<'. 'cut' removes the first two characters added by 'diff', that are not part of the original content.

The files don't even need to be sorted.