Скачать или смотреть How to Run Regex Against the Third Column Only Using Sed

Learn how to use GNU sed with regex to modify the third column of your text file, filtering out specific number patterns for an organized output.
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How to Run Regex Against the Third Column Only Using Sed

In the world of data processing, running a regex against specific columns in a text file can be crucial for extracting and formatting information effectively. If you're working with a file that has multiple columns, you might find yourself needing to target only one column for transformation, especially if it contains various numbers and text. In this guide, we'll walk you through how to filter the third column of a file using GNU sed and regex.

Problem Overview

Let's say you have a file named content.txt containing three columns. The first column represents dates, the second represents times, and the third column contains random text and a mix of numbers. Here's how a sample entry looks:

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

Your goal? To extract specific strings of numbers from the third column while discarding everything else. You are particularly interested in numbers that start with 9, are followed by one of the digits 4, 5, 6, 7, or 9, and continue with six more digits.

Regex Breakdown

The regex pattern we are going to use is:

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

9* ensures that the string begins with a 9.

[45679] follows the initial 9 with one of the specified digits.

( *[0-9]){6} indicates that the string should continue with six digits, which may be separated by spaces.

Using Sed to Perform the Transformation

To run this regex against the third column, we will utilize GNU sed. Here’s the command you'll need:

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

Explanation of the Sed Command

-E: This flag enables extended regex syntax.

s/....../....../: This is the main substitution command.

^(.{16}): Captures the first 16 characters, which includes date and time.

.*: Matches everything else in the line.

( 9[45679]( *[0-9]){6}): Captures the desired number pattern from the third column.

\1\2: Replaces the entire line with the captured date, time, and filtered number pattern.

s/ //g: This second substitution command removes any spaces from the output.

Output

When you run the sed command on your file, you should get the following output, with the third column modified according to your regex:

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

Conclusion

With this simple command using GNU sed, you've successfully transformed the third column of your text file to display only the patterns that match your regex, neatly formatted with no spaces. Mastering this technique can significantly enhance your data manipulation skills in text processing.

Feel free to explore more about sed and regex by checking the manual page using the command man sed. Happy coding!