Man Pages

Linux distributions include man pages for most standard commands, system calls, and standard library functions.The man pages are divided into numbered subsections; for programmers, the most important are these:

(1) User commands
(2) System calls
(3) Standard library functions
(8) System/administrative commands

The numbers denote man page subsections. Linux's man pages come installed on your system; use the man command to access them. To look up a man page, simply invoke man name, where name is a command or function name.

% man sleep
% man 3 sleep

If you're not sure which command or function you want, you can perform a keyword search on the summary lines, using man -k keyword.