{{tag>howto find information commands man apropos info whatis help}}
====== find information about commands ======
Main sources for info and all parts of the operating system are:
  * man - [[pages:man:man]]
  * info - [[pages:man:info]]
  * apropos
  * whatis
  * help (for Bash Builtins)
  * Package documentation at /usr/share/docs/<package>

<note tip>is likely to be forgotten:
<sxh bash; gutter: false>
<command> --help
</sxh>
</note>

===== Introduction to the --help Option =====
Another important source of Linux documentation is use of the --help option.

Most commands have an available short description which can be viewed using the --help or the -h option along with the command or application. For example, to learn more about the man command, you can run the following command: 
<sxh bash; gutter: false>
man --help
</sxh>

The --help option is useful as a quick reference and it displays information faster than the man or info pages.

===== The help Command =====
Some popular commands (such as echo), when run in a bash command shell, silently run their own built-in versions of system programs or utilities, because it is more efficient to do so. To view a synopsis of these built-in commands, you can simply type help.

For these built-in commands, help performs the same basic function as the -h and --help arguments (which we will discuss shortly) perform for stand-alone programs.

===== Online Resources =====
There are many places to access online Linux documentation, and a little bit of searching will get you buried in it. The following site has been well reviewed by other users of this course and offers a free, downloadable command line compendium under a Creative Commons license:

  * LinuxCommand.org: http://linuxcommand.org/tlcl.php

You can also find very helpful documentation for each distribution. Each distribution has its own user-generated forums and wiki sections. Here are just a few links to such sources:

  * Ubuntu: https://help.ubuntu.com/
  * CentOS: https://www.centos.org/docs/
  * OpenSUSE: http://en.opensuse.org/Portal:Documentation
  * GENTOO: http://www.gentoo.org/doc/en

Moreover, you can use online search sites to locate helpful resources from all over the Internet, including blog posts, forum and mailing list posts, news articles, and so on.

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~~DISCUSSION~~