Plumbing

Plumbing: Pipes: |, Three Streams: Output, Errors and Input.

Updated November 10, 2026

1. Pipes: | (Apprentice): The pipe, |, hands everything one command prints to the next command as its input, so small commands that each do one job join into a pipeline that answers a question none of them can answer alone.
2. Three Streams: Output, Errors and Input (Apprentice): Every command has three streams, output, errors and input, and redirection sends each where you choose, with 2> for errors, &> or > file 2>&1 for both together, /dev/null to throw them away and < to read a file in.