CIS120 Linux Fundamentals by Scott Shaper

Apropos, Info and Whatis Commands

Think of these commands as your Linux documentation toolkit. When you're not sure which command to use, or need to understand what a command does, these tools help you find the right information quickly.

Quick Reference

Command Description Common Use
apropos Search for commands by description When you know what you want to do but not the command name
info View detailed documentation When you need comprehensive information about a command
whatis Show one-line descriptions When you need a quick summary of what a command does

apropos Command

The apropos command is like a search engine for Linux commands. It helps you find commands when you know what you want to do but can't remember the exact command name.

When to Use apropos

Use apropos when you want to:

Common Options

Option What It Does When to Use It
-a Match all keywords When you want to narrow down results
-e Exact word matching When you want precise results
-s Search specific sections When you want to focus on certain types of commands
-w Match whole words When you want to avoid partial matches

Practical Examples

Basic Search
# Find commands related to copying
apropos copy

# Find commands about files
apropos file

# Find commands about networking
apropos network
Advanced Search
# Find commands that match both 'file' and 'copy'
apropos -a file copy

# Search only in section 1 (user commands)
apropos -s 1 copy

# Find exact matches for 'copy'
apropos -e copy

info Command

The info command is like an interactive textbook for Linux commands. It provides detailed documentation that's often more comprehensive than man pages, with a structure similar to a website.

When to Use info

Use info when you want to:

Common Options

Option What It Does When to Use It
--apropos Search all info pages When you want to find information across all docs
--directory Add custom info directory When you have additional documentation
--output Save to file When you want to read documentation later

Navigation Tips

Key What It Does When to Use It
h Show help When you need to see all navigation options
Space Next page When reading through documentation
Backspace Previous page When you want to go back
n Next node When moving to the next section
p Previous node When returning to previous section
u Up one level When you want to go back to the main menu
m Open menu When you want to jump to a specific section
q Quit When you're done reading

Practical Examples

Basic Usage
# View info for bash
info bash

# Search all info pages
info --apropos "regular expression"

# Save info to a file
info bash --output=bash-info.txt

whatis Command

The whatis command is like a quick dictionary for Linux commands. It gives you a one-line description of what a command does, perfect for when you need a quick reminder.

When to Use whatis

Use whatis when you want to:

Common Options

Option What It Does When to Use It
-w Match whole words When you want precise matches
-r Use regular expressions When you want flexible matching
-s Search specific sections When you want to focus on certain types of commands

Practical Examples

Basic Usage
# Get description of ls
whatis ls

# Search for commands about files
whatis -r "file.*"

# Check commands in section 1
whatis -s 1 ls

Tips for Success

Common Mistakes to Avoid

Best Practices