zet: Take the union, intersection, etc of files

This is a command-line utility for doing set operations on files considered as sets of lines. For instance, zet union x y z outputs the lines that occur in any of x, y, or z. Two notes:

• Each output line occurs only once, because we're treating the files as sets and the lines as their elements.
• We do take the file structure into account in one respect: the lines are output in the same order as they are encountered. So zet union x prints out the lines of x, in order, with duplicates removed.

Here are the subcommands of zet and what they do:

• zet union x y z outputs the lines that occur in any of x, y, or z.
• zet intersect x y z outputs the lines that occur in all of x, y, and z.
• zet diff x y z outputs the lines that occur in x but not in y or z.
• zet single x y z outputs the lines that occur in exactly one of x, y, or z.
• zet multiple x y z outputs the lines that occur in two or more of x, y, and z.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.