February 2004
Beginner
200 pages
5h 40m
English
Most Linux programs accept data from standard input, which is usually your keyboard, and produce output on standard output, which is usually your screen. Additionally, error messages are usually displayed on standard error, which also is usually your screen but kept separate from standard output.[2] Later we’ll see how to redirect standard input, output, and error to and from files or pipes. But let’s get our vocabulary straight. When we say a command “reads,” we mean from standard input unless we say otherwise. And when a command “prints,” we mean on standard output, unless we’re talking about computer printers.
[2] For example, you can capture standard output in a file and still have standard error messages appear on screen.