How to Read Manual Pages in Linux | man Command

The "man" command, short for manual, is a powerful tool in the Linux operating system that allows users to access detailed information about various commands, utilities, and system calls. The "man" command provides comprehensive documentation, helping users understand how to use and configure different elements of the Linux environment. This article will explore the "man" command in detail, covering its syntax, and options, and providing practical examples.

What is man in Linux Command?

The man command in Linux is used to display the manual pages for other commands and utilities. It provides detailed documentation about the usage, options, and functionality of commands, making it an essential tool for both beginners and experienced users. Each manual page includes sections such as NAME, SYNOPSIS, DESCRIPTION, OPTIONS, and EXAMPLES, which help users understand and effectively use the command.

Description

The man command is essentially the Linux manual reader. When you type man followed by a command name, it retrieves and displays the manual page for that command, offering comprehensive details on how to use it, including all available options and flags. This command is crucial for learning about the tools and commands available in the Linux operating system.

Syntax of the "man" Command

The basic syntax of the "man" command is as follows:

man [option] [command]

Here,

"option" refers to additional flags that modify the behavior of the "man" command,

"command" is the Linux command or utility for which you want to access the manual.

Man Command Options

The "man" command itself has options that enhance its functionality:

Accessing Manual Pages

• To access the manual page for a specific command, simply type:

man [command]

For example: To view the manual for the "ls" command execute the following command:

man ls

• This will display detailed information about the "ls" command, including its usage, options, and examples.

Navigating Manual Pages

Once you've accessed a manual page, you can navigate through it using various commands. The common navigation keys include:

• Spacebar: Move forward one page.
• Enter: Move forward one line.
• B: Move backward one page.
• Q: Quit the manual viewer.

Sections in Manual Pages

Manual pages are organized into different sections, each serving a specific purpose. The primary sections include:

• NAME: Provides the name and a brief description of the command.
• SYNOPSIS: Describes the syntax of the command.
• DESCRIPTION: Offers a detailed explanation of the command's functionality.
• OPTIONS: Lists the available command-line options and their descriptions.
• EXAMPLES: Provides practical examples demonstrating command usage.
• SEE ALSO: Suggests related commands or resources.

Types of sections in Man command Manuals

The man command manuals are divided into several sections, each providing specific types of information about the commands and features of the Linux operating system. Understanding these sections helps users navigate the extensive documentation efficiently. Every manual is divided into the following sections:

1. Executable programs or shell commands: Commands that can be executed in the shell, like ls, cd, or grep.
2. System calls: Functions provided by the kernel, such as open, read, and write.
3. Library calls: Functions within program libraries, like those in the C standard library, such as printf and malloc.
4. Games: Documentation for games available on the system.
5. Special files: Usually found in /dev, these include device files like /dev/null and /dev/sda.
6. File formats and conventions: Details on file formats and conventions, e.g., /etc/passwd.
7. Miscellaneous: Including macro packages and conventions, e.g., groff(7).
8. System administration commands: Commands typically used by the root user for system administration tasks, like iptables or mount.
9. Kernel routines: Non-standard kernel routines used within the system.

Examples of Man Command section types with Detailing

The following are the examples of man command section types with detailing:

1. Section-num in man Command in Linux

• In the man command manuals, sections are used to categorize different types of information. You can specify a section number to display only the relevant section of a manual.

Syntax

man [SECTION-NUM] [COMMAND NAME]

Example

man 2 intro

Output

This command displays the manual entry for the intro in section 2, which pertains to system calls. Specifying a section number ensures you get the precise information you need from the extensive Linux manual pages.

• In this example, the manual pages of command 'intro' are returned which lies in the section 2.

2. -f option in man Command in Linux

• One may not be able to remember the sections in which a command is present. So this option gives the section in which the given command is present.

Syntax

man -f [COMMAND NAME]

Example

man -f ls

Output

This command lists the sections where the ls command appears, indicating that ls is documented in section 1.

3. -a option in man Command in Linux

• This option helps us to display all the available intro manual pages in succession.

Syntax

man -a [COMMAND NAME]

Example

man -a intro

Output

This command will show all intro manual pages one after the other, allowing you to cycle through them to find the specific information you need. This is useful for viewing multiple sections that a command might be documented in.

• The following screenshot illustrate on the manual pages of intro of section 2:

In this example you can move through the manual pages(sections) i.e either reading(by pressing Enter) or skipping(by pressing ctrl+D) or exiting(by pressing ctrl+C).

4. -k option in man Command in Linux

The -k option in the man command allows you to search for a command as a regular expression across all manual pages, returning a list of matching entries along with their section numbers.

Syntax

man -k [COMMAND NAME]

Example

man -k cd

Output

This command searches for the term "cd" in all manual pages and displays the relevant entries along with the sections where they are found. This is useful for finding related commands and topics within the manual pages.

• The command 'cd' is searched in all the manual pages by considering it as a regular expression.

5. -w option in man Command in Linux

• The -w option in the man command returns the location of the manual page for a given command. This is useful for finding where the manual pages are stored on the system.

Syntax

man -w [COMMAND NAME]

Example

man -w ls

Output

In this example, the command man -w ls outputs the path to the manual page for the ls command, indicating where the documentation file is located on the system.

• The location of command 'ls' is returned.

6. -I option in man Command in Linux

The -I option in the man command makes the search case-sensitive, ensuring that the command name is considered with exact case.

Syntax

man -I [COMMAND NAME]

Example

The execution of following command helps in finding the manuals of printf command with case sensitiveness.

man -I printf

Output

This command searches for the manual pages of the printf command, treating the command name with case sensitivity. This is useful when differentiating between commands or sections that have similar names but different cases.

• The following screenshot illustrates the manual of printf command with case -sensitive:

• The following looks for the manual pages for Printf command with case sensitive:

• The command 'printf' is taken as case-sensitive i.e 'printf' returns the manual pages but 'Printf' gives error.

How to Search Manual Pages in Linux?

There are three main ways:

1. Using the `man` command: This is the classic approach. Type `man` followed by the command name to find its manual page. For example, `man mkdir` will show you the manual page for the `mkdir` command.
2. Using the `-k` option: Want to search for keywords across all manual pages? Use man -k followed by your keyword(s). For instance, `man -k permissions` will find pages mentioning "permissions".
3. Using the `apropos` command: Similar to `man -k`, but `apropos` also searches descriptions, not just names. Try `apropos networking` to find pages related to networking.

Alternative ways to read man pages

The following are the alternative ways to read man pages:

• man2html: Converts man pages to HTML format, which can be easier to read on a graphical user interface (GUI).
• tldr: Provides shorter, simplified versions of man pages.
• whatis: Gives a very brief one-line summary of a command.
• apropos: Searches the man pages for keywords and provides a list of commands and their brief descriptions.
• info: Displays more detailed and hyperlinked documentation about commands and programs, often including more background information than man pages.

Conclusion

In this article we discussed the "man" command in Linux which is an essential tool for accessing detailed documentation on commands, utilities, and system calls. It provides a comprehensive guide with organized sections, including syntax, options, and examples. With options like -f, -k, and -a, users can quickly retrieve concise descriptions, search related commands, and access all matching manual pages.

Navigating through manual pages is simplified with common keys like Spacebar and Enter. The "man" command is not just a documentation tool; it is a valuable resource for users of all levels, contributing to a better understanding of Linux commands and enhancing command-line proficiency.