Frequently Asked Question

Who invented the Unix pipe?

The idea is Doug McIlroy's. As head of the computing research department at Bell Labs in the late 1960s he kept arguing that programs ought to "fit together like garden hose", with the output of one snapped onto the input of the next. He wrote a series of memos urging the operating-system group to add something along those lines. The implementation arrived on the evening of 3 January 1973, when Ken Thompson, after one of McIlroy's tirades, sat down and rewrote much of the shell to support the syntax overnight.

The choice of the vertical bar | as the operator was a small detail with enormous consequences. Doug McIlroy then went on to write the small tools that proved the idea: spell, diff, sort, join, tr, tsort, comm. The Bell Labs Unix group spent the next year converting almost every existing tool to read from stdin and write to stdout so they could be plugged into the new mechanism, and the modern command line was born. McIlroy himself called it "one of the few really inventive things that we did".