The Unix pipe (|) is so fundamental it’s easy to forget someone had to invent it. That someone was Doug McIlroy, who in 1964 sketched a memo proposing that programs should be able to pass output directly to other programs, like water through a garden hose. It took nearly a decade for Ken Thompson to implement it overnight in 1973, cutting a notch in the wall of the Unix kernel to let data flow between processes. The pipe transformed Unix from a collection of utilities into a composable toolkit — and gave rise to the Unix philosophy of small, sharp tools doing one thing well. McIlroy himself later grumbled that even Unix didn’t fully live up to the ideal. He was right, of course, but grep foo | sort | uniq -c | sort -rn remains one of computing’s small everyday pleasures.
