man

Definition:

man is used to format or display the manual pages. Manual pages or man pages are the official documentation of all shell commands that comes along with the Linux distributions.

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Syntax:

man [option(s)] keyword(s)

In order to display manual page from specific section:

man [section-num] [command/tool name]

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Section Numbers:

Section No.	Section Description
1	Programs or shell commands
2	System calls (functions provided by the kernel)
3	Library calls (functions within program libraries)
4	Special files (usually found in /dev)
5	File formats and conventions eg /etc/passwd
6	Games and demonstrations
7	Miscellaneous (including macro packages and conventions), e.g., man, groff
8	System administration commands (usually only for root)
9	Device driver interfaces

Options:

Option	Syntax	Meaning
-s	man <section num> <command>	To specifically view a section of a man page.
-a	man -a <command>	To display all manual pages where a command exists.
-w	man -w [command/tool name]	To view the location for man pages.
-I	man -I [command/tool name]	To enable case-sensitivity while searching for man pages
-H	man -H[browser-command] [command/tool name]	To display manual pages in web browser.
-f	man -f [command/tool name]	To lookup for manual pages and display short descriptions as well.

Example:

To get information about the ls command:

man ls