How to Store lsblk Command Output in a Bash Associative Array

Описание: Learn how to process `lsblk` command output and store it in a structured associative array in Bash for easy access and manipulation.
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This video is based on the question https://stackoverflow.com/q/66274650/ asked by the user 'Hrishikesh Kadam' ( https://stackoverflow.com/u/3302026/ ) and on the answer https://stackoverflow.com/a/66281625/ provided by the user 'markp-fuso' ( https://stackoverflow.com/u/7366100/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering Bash: Storing lsblk Command Output in an Associative Array

When working with Linux systems, the lsblk command is incredibly useful for listing block devices and their properties. However, you might want to extract specific pieces of information and store them in a more structured format, such as an associative array in Bash. This allows for straightforward access to attributes like mount points, labels, and UUIDs. In this guide, we'll walk through the steps to achieve that.

The Challenge

Suppose you have the following output from the lsblk command:

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You want to store this data in an associative array named partition so that:

partition[MOUNTPOINT] contains /media/user/GParted Live

partition[LABEL] contains GParted Live

partition[UUID] contains xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

So how do we convert this raw output into a structured array? Let’s dive into the solution using a well-organized Bash script.

Step-by-Step Solution

1. Prepare Your Input Data

For this example, we'll assume we have the lsblk output stored in a file called lsblk.out. The contents look like this:

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2. Using sed to Format the Output

To start, we need to format the output properly. The goal is to transform the single line of lsblk output into separate lines for each key-value pair. We can achieve this using sed:

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This command uses a regular expression to match each key-value pair and outputs them on separate lines.

3. Reading and Storing in Associative Array

With the formatted output ready, we can then read each line into our associative array. Here’s how you can do it:

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4. Verifying the Results

Now that we’ve populated the array, let's verify that our associative array contains the expected values:

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This will print the contents of the partition array, allowing you to confirm everything is stored correctly.

5. Displaying the Contents

To display the values stored in the array neatly, you can loop through the keys like this:

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This will output each key along with its corresponding value:

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6. Stripping Double Quotes (Optional)

If you’d like to remove the double quotes surrounding the values, you can modify the read operation like this:

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This replaces double quotes with nothing, giving you clean values.

7. Using lsblk Directly

You can also feed the lsblk command directly without saving its output to a file:

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Conclusion

By following the above steps, you now have the necessary knowledge to take raw output from the lsblk command and store it in a structured associative array for easier access and manipulation in your Bash scripts. Associative arrays provide a powerful way to manage data in a recognizable and accessible format, making your scripts cleaner and more efficient.

Feel free to test the provided code snippets in your own environment to see how they work in action. Happy scripting!