That quote is actually by Doug McIlroy, who also gave this longer phrasing of it: "Expect the output of every program to become the input to another, as yet unk

That quote is actually by Doug McIlroy, who also gave this longer phrasing of it: "Expect the output of every program to become the input to another, as yet unknown, program. Don't clutter output with extraneous information. Avoid stringently columnar or binary input formats. Don't insist on interactive input."