Why You Should Live in the Manual

Linux ships with extensive built-in documentation. Mastering help commands turns the shell into a self-teaching environment.

1. man — The Manual

The man (manual) command displays a structured page about a command, system call or configuration file.

Sections:

Inside man, use /pattern to search and q to quit.

2. info — GNU Hypertext Documentation

GNU programs ship richer info pages with hyperlinks and a node tree. Navigate with n (next), p (previous), u (up), q (quit).

3. --help Flag

Almost every modern command supports --help to print a short summary and option list. Built-in shell commands like cd and alias use the bash help builtin instead, because they have no man page of their own.

4. whatis — One-line Description

whatis queries the man-page database for a one-line description. Run mandb once if the database is empty.

5. apropos — Search by Keyword

When you don't know the exact command, apropos keyword (same as man -k keyword) searches the short descriptions of all man pages for that keyword.

Quick Reference Table

Worked Example

You vaguely recall a command that compresses files but cannot remember its name:

apropos compress lists candidates: gzip, bzip2, xz, zip. You then run man gzip for details.

Summary

Use man and info for depth, --help and help for speed, and apropos/whatis to discover commands you don't know.