You can use comm from coreutils for that too: `comm -1 file1 file2`
1. http://manpages.ubuntu.com/manpages/zesty/en/man1/comm.1.htm...
Ah, HN downvoting neutral comments again and I don't like it, but I have a policy of not upvoting anything out of pity.
PS: do not worry about karma ^^