There's a standard POSIX utility that does that: comm. It assumes your files are sorted (but if not, that's easy to do). In bash, you can write: 
comm <(sort file1) <(sort file2)

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and it prints three columns, one with lines only in file1, one with lines only in file2, and one with lines in both files.

In reply to Re: Comparing the contents of two files by JavaFan
in thread Comparing the contents of two files by archer

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