Wire one program's output into another's input.
In this interactive Linux lesson from Stencel Academy you don't just read — you type real commands like ls | grep txt, ls notes.txt 2>&1 and watch the machine respond on a live, animated map. It is part of the free How Linux Works course.
Builds on: Signals.
ls | wc -l — Count lines flowing through the pipe.ps aux | grep ssh — The classic: filter another command's output.ls | sort -r | head -1 — Chain as many stages as you like.ls | tee files.txt | wc -l — tee splits the stream: to a file AND onward.