Understanding a Program's Info Entry in Linux and How to Use the `info` Command

Introduction

In the Linux ecosystem, understanding how to effectively navigate and use documentation is crucial. While man pages are often the go-to for quick reference, the info utility offers a more detailed and organized view of documentation. In this article, we'll explore what an info entry is, how to navigate it, and the different ways the info command can be used.

What is an Info Entry?

The GNU Info system was developed to provide detailed, structured documentation for programs, functions, and libraries. It serves as a supplement, or in some cases, a replacement, for traditional man (manual) pages. Info entries are usually more extensive than man pages and are structured as hyperlinked documents that can be easily navigated, much like web pages.

Info entries are stored in the .info format and are commonly found in /usr/share/info/ or /usr/local/share/info/.

How to Use the info Command

To launch the info browser and start reading the documentation for a particular command, library, or program, you can simply type:

info [topic]

where [topic] is the name of the program, command, or library you want to learn about.

Navigation Keys

• Space: Scroll down
• Delete or Backspace: Scroll up
• n: Next node
• p: Previous node
• u: Up one level
• q: Quit info browser

Examples

Viewing General Info Directory

info

This command opens the top-level directory of all available Info documentation.

Viewing Info Entry for a Specific Command (e.g., ls)

info ls

This command opens the Info entry for the ls command, displaying detailed information on its usage, options, and examples.

Searching for Commands Containing a Keyword

info --apropos=keyword

This searches for all info entries that have keyword in their metadata or content and displays a list of matches.

Viewing a Specific Section of an Entry

info 'ls#OPTIONS'

This command jumps directly to the "OPTIONS" section of the ls info page.

View Info Entry as Plain Text

info --subnodes -o out.txt ls

This saves the Info entry for ls, including all its subnodes, to out.txt in plain text format.

Table of info Commands

Command	Detailed Explanation
info	Opens the top-level Info directory
info [topic]	Opens the Info page for the specified topic
info --apropos=keyword	Searches for Info entries containing keyword
info -k keyword	Alias for --apropos, searches for keyword
info --subnodes	Includes all subnodes when displaying an entry
info --output=file	Redirects output to a file
info --where	Prints the location of the Info file for a topic
info --vi-keys	Enables vi-like key bindings

man vs info

Feature	info Command	man Pages
Structure	Hyperlinked, tree-like structure	Linear, scrollable text
Navigation	Navigate through hyperlinks and nodes	Scroll up and down
Detail Level	Usually more detailed, covers the topic exhaustively	Tends to be concise, providing essential information
Interactivity	More interactive, resembling a basic web browser	Mostly static text, less interactive
Search Functionality	Can search within the document and navigate to specific nodes	Can search within the page, but lacks hyperlinking
Examples	Often contains examples, especially for complex commands	May contain examples, but usually fewer and less detailed
File Format	Stored in .info files	Stored in .gz files (compressed groff text)
File Location	Usually in /usr/share/info/ or /usr/local/share/info/	Usually in /usr/share/man/
Multimedia Elements	May contain menus and ASCII art	Generally plain text, lacking multimedia elements
Command Options	Various options like --apropos, --subnodes, --output, etc	Fewer options, primarily focuses on displaying the manual page
User Experience	Designed for in-depth reading and learning	Suitable for quick look-ups and command synopsis
History	Developed by the GNU Project as an enhancement to man	Traditional Unix documentation system

Conclusion

The info command provides a structured, detailed, and navigable way to access documentation on Linux systems. Whether you're a beginner looking for guided explanations or an experienced user in need of a quick reference, info is an invaluable tool. Familiarizing yourself with info entries and commands can greatly enhance your proficiency in Linux.

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