How to Access Command Documentation in Linux

Linux provides various methods for accessing documentation on commands, ranging from simple help prompts to detailed manual pages (man) and hyperlinked info pages. Understanding these tools allows users to efficiently search for command details, syntax, and options.
This article explores different ways to retrieve command documentation, including help, --help, man, apropos, whatis, and info.
Using help for Shell Builtins The help command provides built-in documentation for shell commands (builtins) in Bash.
Syntax Here, command is the name of a shell builtin (e.g., cd, echo, exit).
Example: Getting Help on cd The output provides detailed usage information, including available options and exit status codes.
Using --help for Executable Programs Many Linux commands support the --help option, which provides a brief usage guide.
Syntax This works for executable programs (e.g., mkdir, cp, ls) but not for shell builtins.
Example: Getting Help on mkdir The output typically includes: Command usage Available options Error reporting instructions
Using man for Detailed Manual Pages Most command-line programs have manual pages (man pages), which serve as formal documentation.
Syntax This opens the manual page for the specified program.
Example: Viewing the ls Manual Page Man pages contain: Command description Syntax overview Detailed options explanation Exit status codes
Man Page Sections Linux man pages are categorized into eight sections:

Section	Contents
1	User commands
2	Programming interfaces for kernel system calls
3	Programming interfaces for the C library
4	Special files like device nodes and drivers
5	File formats
6	Games and screen savers
7	Miscellaneous documentation
8	System administration commands

Searching Man Pages in a Specific Section If a search term appears in multiple sections, specify the section number: This opens the file format documentation for /etc/passwd.
Using apropos for Keyword Searches The apropos command searches man pages for relevant keywords.
Syntax Where keyword is the search term.
Example: Searching for Partition-related Commands Returns matching man pages, including disk partition utilities (fdisk, cfdisk).
Using whatis for One-line Descriptions The whatis command provides a short description of a command.
Syntax Where command is the program name.
Example: Checking ls Description Returns: bash ls (1) - list directory contents This confirms that ls belongs to section 1 (user commands).
Using info for Hyperlinked Documentation The GNU Project offers an alternative to man pages called info, which uses a hyperlinked structure similar to web pages.
Syntax Opens the info documentation for the specified command.
Example: Viewing coreutils Info Pages Displays a structured reference covering multiple utilities in GNU Coreutils.
Navigation Commands for info Pages

Command	Action
?	Show help menu
Page Up / Backspace	Move to previous page
Page Down / Space	Move to next page
n	Go to next section
p	Go to previous section
Q	Exit the info page

Conclusion Linux offers multiple ways to access documentation, each suited for different use cases: Use help for built-in shell commands. Use --help for quick command usage summaries. Use man for detailed reference manuals. Use apropos to search related commands. Use whatis to view one-line command descriptions. Use info for structured documentation with hyperlinks.