Apropos Linux Command Explained {With Examples}

If you're someone who frequently uses Linux, you may have come across term 'apropos' while using terminal. Apropos is a very useful Linux command that helps users find commands related to a specific topic or keyword. In this article, we will take a closer look at 'apropos' command and explain its usage with several examples.

What is Apropos?

'Apropos' is a command-line utility in Linux that searches manual pages for a keyword or topic and returns a list of relevant commands. It is a great tool for quickly finding commands you need, especially if you don't remember exact command name.

The 'apropos' command works by searching 'man' pages, which are Linux manual pages that contain documentation for various commands, utilities, and system calls. These manual pages are organized by sections, and 'apropos' command searches all of sections for specified keyword.

How to use Apropos?

The syntax for using 'apropos' command is simple: apropos <keyword>

For example, if you want to search for all commands related to "network", you can type −

apropos network

This will return a list of all commands related to keyword "network", along with a brief description of each command.

Examples of Apropos Usage

Let's take a look at some examples of how 'apropos' command can be used in different situations.

Example 1: Finding all Commands Related to a Keyword

As mentioned earlier, most common usage of 'apropos' command is to find all commands related to a specific keyword or topic. Let's say you want to find all commands related to "file". You can type following command −

apropos file

This will return a list of all commands related to "file", such as 'cat', 'cp', 'ls', 'mv', 'rm', and many more. list will also include a brief description of each command, making it easier for you to decide which command to use.

Example 2: Finding a Specific Command

Sometimes, you may know name of command you need, but you may not remember its exact syntax or usage. In such a case, you can use 'apropos' command to find command you need.

For example, let's say you want to use 'grep' command, but you don't remember its syntax. You can type following command −

apropos grep

This will return 'grep' command along with a brief description of its usage. You can then use 'man' command to learn more about 'grep' command and how to use it.

Example 3: Finding a Command by Description

In some cases, you may remember description of a command but not its exact name. In such a case, you can use 'apropos' command to search for command by its description.

For example, let's say you remember that there is a command that can be used to find largest file in a directory, but you don't remember its name. You can type following command −

apropos "largest file"

This will return 'du' command, which can be used to find size of a directory or file. You can then use 'man' command to learn more about 'du' command and how to use it to find largest file in a directory.

Example 4: Finding all Available Options for a Command

Sometimes, you may want to find all available options for a specific command. You can use 'apropos' command to search for command and then use 'man' command to see all available options.

For example, let's say you want to find all available options for 'ls' command. You can type following command −

apropos ls

This will return 'ls' command along with a brief description of its usage. You can then use 'man' command to see all available options for 'ls' command. To do this, type −

man ls

This will display manual page for 'ls' command, which includes a list of all available options along with their descriptions.

Tips for Using Apropos

Here are a few tips for using 'apropos' command more effectively −

• Be specific with your search terms − 'apropos' command will return a lot of results if your search term is too broad. Try to be as specific as possible when searching for commands.

• Use quotes for multiple keywords − If you're searching for commands related to multiple keywords, enclose them in quotes. For example, to search for commands related to both "network" and "security", you can type: apropos "network security"

• Use -a option for more results − By default, 'apropos' command only returns first 10 results. If you want to see more results, you can use '-a' option. For example, apropos -a network will return all commands related to "network".

• Use -w option for exact matches − If you want to search for commands that match your search term exactly, use '-w' option. For example, apropos -w grep will only return 'grep' command and not other commands that contain word "grep".

• Use -k option for keyword search − If you're not sure about exact command name but know a keyword that might be used in command, you can use '-k' option. For example, apropos -k "search pattern" will return all commands related to searching for patterns.

Apropos in Shell Scripting

The 'apropos' command can also be used in shell scripting. In a shell script, you can use 'apropos' command to find command you need and then use it in your script.

For example, let's say you're writing a shell script that needs to search for a specific pattern in a file. You can use 'apropos' command to find 'grep' command and then use it in your script.

#!/bin/bash

# Find 'grep' command
GREP_COMMAND=$(apropos -w grep | awk '{print $1}')

# Use 'grep' command to search for a pattern in a file
$GREP_COMMAND "pattern" file.txt

In this example, 'apropos' command is used to find 'grep' command, which is then assigned to 'GREP_COMMAND' variable. 'grep' command is then used to search for a pattern in a file.

Apropos vs. Man

While 'apropos' command is a useful tool for finding commands related to a specific topic, it's important to note that it's not a replacement for 'man' command. 'man' command provides detailed documentation for each command, including usage examples, options, and syntax.

The 'apropos' command, on other hand, only provides a brief description of each command and its purpose. It's a useful tool for finding commands, but it doesn't provide same level of detail as 'man' command.

Apropos Alternatives

While 'apropos' command is a useful tool for finding commands related to a specific topic, there are some alternative tools you can use as well.

One alternative is 'whatis' command, which provides a brief description of a specific command. For example, if you want to know what 'ls' command does, you can type −

whatis ls

This will return a brief description of 'ls' command, such as "list directory contents".

Another alternative is 'man -k' command, which works in a similar way to 'apropos' command. To search for commands related to a specific topic, you can type −

man -k <keyword>

This will return a list of all commands related to specified keyword, along with a brief description of each command.

Apropos in Conjunction with Wildcards

The 'apropos' command can also be used in conjunction with wildcards to find commands related to a specific pattern. This can be particularly useful when you want to find all commands related to a certain type of file or operation.

For example, to find all commands related to file compression, you can use following command −

apropos "*compress*"

This will return all commands related to file compression, such as 'gzip', 'bzip2', 'zip', and many others.

Similarly, you can use 'apropos' command to find all commands related to a specific type of file. For example, to find all commands related to image files, you can use following command −

apropos "*image*"

This will return all commands related to image files, such as 'convert', 'identify', 'mogrify', and others.

Conclusion

The 'apropos' command is a powerful and versatile tool that can help you find commands you need quickly and easily. Whether you're searching for a specific command, trying to find all available options for a command, or looking for commands related to a specific topic, 'apropos' command can help you get job done. So, next time you're working in Linux terminal and need help finding a command, remember to use 'apropos' command!