union (https://github.com/sixarm/union): print lines in (A union B)

intersect (https://github.com/sixarm/intersect): print lines in (A intersect B)

except (https://github.com/sixarm/except): print lines in (A except B) a.k.a. (A - B)

extra (https://github.com/sixarm/extra) : print lines in (A extra B) a.k.a. (B - A)

Examples:

    $ cat 1.txt
    alpha
    bravo

    $ cat 2.txt
    alpha
    charlie

    $ union 1.txt 2.txt
    alpha
    bravo
    charlie

    $ intersect 1.txt 2.txt
    alpha

    $ except 1.txt 2.txt
    bravo

    $ extra 1.txt 2.txt
    charlie