Non greedy (reluctant) regex matching in sed?

📝 Title: Non-greedy (Reluctant) Regex Matching in sed: How to Extract Domains from URLs 🌐

👋 Hey there tech enthusiasts! Today, we're diving into the sed command and how to use it to extract domain names from URLs. If you've ever struggled with non-greedy (reluctant) regex matching in sed, fret not! We've got you covered. Let's get started! 🚀

🤨 The Challenge: Extracting Domains from URLs

So, you have a bunch of URLs, and all you want is to extract the domain name. For example, from: http://www.suepearson.co.uk/product/174/71/3816/

You want to extract: http://www.suepearson.co.uk/

🤔 The Attempted Solution: Non-Greedy Quantifiers in sed

You decided to use the sed command, which is a powerful tool for pattern matching and text manipulation. You gave it a shot with the following command:

sed 's|\(http:\/\/.*?\/\).*|\1|'

And even with the escaped non-greedy quantifier:

sed 's|\(http:\/\/.*\?\/\).*|\1|'

But to your dismay, the non-greedy quantifier (?) didn't seem to work as expected; instead, it matched the whole string. 😞

🔍 The Solution: Creative Filtering with Sed

Here's the deal! Sed doesn't support non-greedy quantifiers like Perl or Python. But don't fret! We can achieve our goal in a different way. Let's modify our initial approach and think outside the box. 🧠

Instead of trying to extract the domain directly, let's focus on removing everything after the domain and slash, including the trailing slash if it exists. Here's the tweaked sed command:

sed 's|\(http:\/\/[^/]*\).*|\1|'

Let's break it down to understand what's happening:

• http:\/\/ matches the beginning of the URL.

• [^/]* matches any character that is not a slash, ensuring we don't go beyond the domain.

• .* matches everything else (the path and beyond).

• \1 replaces the whole line with just the domain we captured in the parentheses.

💡 Example Test Run

Using the example URL we started with, here's how the modified sed command looks in action:

echo 'http://www.suepearson.co.uk/product/174/71/3816/' | sed 's|\(http:\/\/[^/]*\).*|\1|'

Output: http://www.suepearson.co.uk

Voila! We sliced out the domain as desired. 😎

💬 Join the Discussion: Your Experience & Thoughts

Have you ever struggled with regex matching in sed? Do you have any alternative solutions that work just as well or even better? Share your experiences and thoughts in the comments below! Let's learn from each other. 👇

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We hope this guide has been helpful in demystifying non-greedy regex matching in sed. If you enjoyed this post and found it valuable, do share it with your fellow tech enthusiasts. Let's spread the knowledge!

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Happy coding! 💻🎉