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Discover how to efficiently replace integers in a string with "EN" or "ENS" using `sed` in Linux. Enhance your scripting skills for text manipulation!
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This video is based on the question https://stackoverflow.com/q/75636626/ asked by the user 'Dr. Coke' ( https://stackoverflow.com/u/20377593/ ) and on the answer https://stackoverflow.com/a/75636922/ provided by the user 'sseLtaH' ( https://stackoverflow.com/u/16372109/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Substitute Integers in a Range of the First 3 Characters with sed

If you've ever struggled with manipulating strings or extracting certain parts of text files, you're not alone! This guide will tackle a specific problem that many Linux users encounter: replacing integers within a specific range of text. Here, we will focus on how to substitute all integers in the first three characters of a string with new values using the popular command-line utility sed.

The Problem

Imagine you have a list of IDs in a file, as shown below:

[[See Video to Reveal this Text or Code Snippet]]

Your goal is to transform this list so that:

If there's 1 integer in the first three characters, it will be replaced with "EN"

If there are 2 integers, it will be replaced with "ENS"

The desired output should look like this:

[[See Video to Reveal this Text or Code Snippet]]

You want to perform this substitution while targeting only the integers in the first three characters. Your previous attempt using a basic sed command didn’t achieve the expected results, and now you're looking for a better solution.

The Solution: Using sed

sed is a powerful stream editor that can perform basic text transformations on an input stream (a file or input from a pipeline). We will use it to solve our problem with a command that cleverly identifies integer patterns and substitutes them accordingly.

The sed Command Breakdown

To achieve the desired output, you can use the following sed command:

[[See Video to Reveal this Text or Code Snippet]]

Let's break down this command:

sed -E: The -E flag allows extended regular expressions, which will help us in matching patterns more easily.

s/^([0-9]{1,2})S?(.*)/ENS\2 \1/: This is the substitution command where:

^([0-9]{1,2}): Matches 1 or 2 digits at the start of the line.

S?: Matches an optional "S" character that might follow the digits.

(.*): Captures the rest of the line that follows the initial matching digits and optional "S".

ENS\2 \1: This replaces the matched string with "ENS" followed by the rest of the line (\2) and then the captured number (\1).

Expected Output

When this command is executed on your input file, it will produce the following output:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Manipulating text using command-line tools like sed can seem daunting at first, but with the right syntax and understanding of regular expressions, you can accomplish complex tasks quickly and efficiently. By targeting specific patterns and making effective substitutions, you can transform your data as needed.

Now, you should feel equipped to tackle similar text processing tasks with sed! If you have any further questions or would like to explore more complex manipulations, feel free to reach out or leave a comment below.