In Linux, there are various programs which provide help with Linux and Linux commands. With how many options there are, it can be difficult to decide which program to use. Here’s a quick cheat sheet to make that decision a bit easier.
| command | information database | description |
|---|---|---|
| man | man pages | manual pages for commands, directories, systems |
| info | info nodes | man pages but more verbose and instructional |
| -h, –help | the command | command option that displays syntax and options |
| help | help | for commands built-in to the Linux shell |
| whatis | whatis database | one-line description of a given command |
| apropos | whatis database | whatis but allows partial command matches |
Man pages are included when installing software.
The whatis database is built from man pages. To initially build the database, run /usr/sbin/makewhatis.
If the man pages are updated, the whatis database won’t automatically update. To update
the database, run makewhatis -u (or whatisupdate on some systems).