Скачать или смотреть Extracting Strings in Shell Script: A Simple Guide Using awk and sed

Learn how to effectively extract the second last column from a CSV file using `awk` and `sed` in your shell scripts. Follow our step-by-step guide for a clearer understanding!
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This video is based on the question https://stackoverflow.com/q/68407534/ asked by the user 'Ankit Goyal' ( https://stackoverflow.com/u/7001109/ ) and on the answer https://stackoverflow.com/a/68407639/ provided by the user 'anubhava' ( https://stackoverflow.com/u/548225/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Extracting Strings in Shell Script: A Simple Guide Using awk and sed

When working with shell scripts, extracting specific strings based on patterns is a common requirement, especially when dealing with CSV files or similar data formats. Let's take a closer look at a scenario where you might be stuck on this very task.

The Problem

Imagine you have a CSV file with multiple lines of records, and your goal is to extract the second last column from each record. If you're using tools like awk or sed, you may find yourself a bit overwhelmed, especially when your attempts don't yield the expected results, as shared in the original inquiry. Here’s what the file content looks like:

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Your expected output, which includes the second last columns, should be:

MxMonitor_Marvel_PI49

alert_manager

MxMonitor_Marvel_PI49

The Solution

Using awk

Take advantage of the powerful awk command to achieve this extraction effectively. Here’s a streamlined approach to extract the needed strings:

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Explanation of the Command:

gsub(/^.*,"|",$//g) is a command within awk that looks for patterns and replaces them.

^.*," matches everything up to the last comma before the desired string.

|,$ matches everything from the last quotation mark to the end of the line.

When you execute this command, you’ll get the following output:

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This is exactly what you are looking for!

Alternatively, Using sed

If you prefer to use sed, you can achieve a similar result with this command:

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Explanation:

s/^.*,"|",.*//g does a substitution similar to the awk command.

It removes everything before and after the string you're interested in.

Summary

In conclusion, extracting strings from a CSV file can be conveniently handled by awk or sed. Both methods will allow you to retrieve the second last column efficiently, reducing the complexity of your script while ensuring you get the desired results.

Tips for Success

Always double-check your input data; any variations can affect your commands' execution.

When manipulating large datasets, consider testing on a smaller file first to ensure your command works as intended.

Harness the power of awk and sed in your shell script to extract the information you need with ease. Happy scripting!