How to Remove Duplicate Words from Multiple Strings in Bash

Learn how to remove duplicate words from each line of a file in Bash using powerful tools like `awk`, `sed`, and more.
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Removing Duplicate Words from Multiple Strings in Bash

Have you ever found yourself dealing with a file filled with duplicate words across multiple lines? It can be quite a hassle! If you have a large file with hundreds or even thousands of lines and want to simplify the content by keeping only unique words, you've come to the right place. This post will guide you through an effective solution using Bash tools like awk and sed. Let’s dive in!

Problem Overview

Imagine you have a file with the following lines:

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The goal is to transform this content to keep just one instance of each unique word per line, resulting in:

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This will make the file cleaner and improve your data's readability.

Solution Using awk

One of the most efficient ways to remove duplicate words in Bash is by using the awk command. Below is a command that can easily accomplish this task:

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Breakdown of the awk Command

Delete Array: The line delete seen initializes an empty array named seen for each line read. This is essential for tracking which words have already been encountered.

Printing the First Column: The command printf "%s", $1 prints the first column (or word) of each line without adding a newline.

Loop Through Words: The for (i=2; i<=NF; + + i) loop iterates through every word in the line, starting from the second word.

Check for Uniqueness: The if (!seen[$i]+ + ) statement checks if the word $i has been seen before. If it hasn’t, it prints the word.

Print Newline: Finally, print "" is used to add a newline at the end of each processed line.

Example with Your Data

When you run the above awk script on your provided data, the output will look like this:

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Additional Tools

Using sed and sort

While awk is highly recommended for this task, you could also use a combination of sort and uniq along with some Bash scripting to achieve similar results. However, this may require additional steps to read file lines one by one and is generally less efficient than the awk solution.

Conclusion

Removing duplicate words from lines in a file can greatly enhance the data’s readability and usefulness. By using the awk command, you can efficiently achieve this, even with large files containing thousands of lines.

Now you have the tools at your disposal to tackle similar problems in the future. Happy scripting! If you have any questions or need further assistance, feel free to reach out!

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