The whatis command is a Linux package that allows users to quickly find the purpose and usage of a specific command. It provides a concise description of the command, making it easier for users to understand its functionality. The whatis package is commonly used by Linux administrators, developers, and users who frequently work with the command line interface.
The whatis package is built using the C programming language. It leverages the Linux manual pages (man pages) to extract information about various commands and their usage. The package is typically pre-installed on most Linux distributions, making it readily available for use.
Installation
The whatis package is usually included in the standard installation of most Linux distributions. However, if it is not available, you can install it using the package manager specific to your operating system.
Debian/Ubuntu
To install the whatis package on Debian or Ubuntu, open a terminal and run the following command:
sudo apt-get install man-db
Red Hat/CentOS
To install the whatis package on Red Hat or CentOS, open a terminal and run the following command:
sudo yum install man-db
Arch Linux
To install the whatis package on Arch Linux, open a terminal and run the following command:
sudo pacman -S man-db
Usage
The whatis command is used to quickly find the purpose and usage of a specific command. It takes the name of the command as an argument and returns a concise description of the command.
Example 1: Finding the description of a command
To find the description of the ls command, open a terminal and run the following command:
whatis ls
The output will be:
ls (1) - list directory contents
The output indicates that the ls command is used to list the contents of a directory.
Example 2: Finding the description of a command with wildcards
The whatis command also supports the use of wildcards to find commands that match a specific pattern. For example, to find all commands that start with “net”, you can run the following command:
whatis net*
The output will be a list of commands that match the pattern:
netcat (1) - TCP/IP swiss army knife
netstat (8) - Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
The output shows that the netcat and netstat commands match the pattern.
Similar Commands
There are several other commands and packages that provide similar functionality to the whatis package. Some of these include:
apropos: This command is used to search the manual pages for commands that match a specific keyword or pattern.man: This command is used to display the manual page for a specific command or topic.help: This command is built-in to the shell and provides help information for shell built-in commands.
While these commands provide similar functionality, the whatis command is specifically designed to provide a concise description of a command, making it easier for users to quickly understand its purpose and usage.
Automation Scripts
Here are three example scripts that demonstrate the use of the whatis command in automation:
Script 1: Find Description of Multiple Commands
This script takes a list of commands as input and uses the whatis command to find their descriptions. The descriptions are then printed to the console.
#!/bin/bash
commands=("ls" "cd" "mkdir")
for command in "${commands[@]}"
do
description=$(whatis $command)
echo "Description of $command: $description"
done
Script 2: Search for Commands with Specific Keyword
This script prompts the user to enter a keyword and uses the whatis command to search for commands that match the keyword. The matching commands are then printed to the console.
#!/bin/bash read -p "Enter a keyword: " keyword matching_commands=$(whatis -w $keyword) echo "Matching commands:" echo "$matching_commands"
Script 3: Generate Command Cheat Sheet
This script generates a cheat sheet of all available commands on the system by using the whatis command. The cheat sheet is saved to a file named “commands.txt”.
#!/bin/bash whatis -s 1,8 -w "*" > commands.txt echo "Command cheat sheet generated successfully."
List of Possible Functions and Constants
| Command/Constant | Description |
|---|---|
| ls | List directory contents |
| cd | Change the current working directory |
| mkdir | Create a new directory |
| rm | Remove files or directories |
| cp | Copy files and directories |
| mv | Move or rename files and directories |
| grep | Search for patterns in files |
| sed | Stream editor for filtering and transforming text |
| awk | Pattern scanning and processing language |
| ssh | Secure shell client for remote login |
Conclusion
The whatis command is a useful tool for quickly finding the purpose and usage of a specific command in Linux. It provides a concise description of the command, making it easier for users to understand its functionality. The whatis package is built using the C programming language and is typically pre-installed on most Linux distributions.
The whatis command is commonly used by Linux administrators, developers, and users who frequently work with the command line interface. It helps them quickly find the information they need without having to search through lengthy manual pages. The whatis command can be used in automation scripts to automate tasks that require finding the description of multiple commands or searching for commands with specific keywords.
Overall, the whatis command is a valuable tool that saves time and improves productivity for Linux users. It is widely used in various industries and sectors, including software development, system administration, and cybersecurity. Whether you are a beginner or an experienced Linux user, the whatis command can help you navigate the vast array of Linux commands and make your work more efficient.
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