RegEx for extracting domains and subdomains

Question

I'm trying to strip a bunch of websites down to their domain names i.e:

https://www.facebook.org/hello 

becomes facebook.org.

I'm using the regex pattern finder:

(https?:\/\/)?([wW]{3}\.)?([\w]*.\w*)([\/\w]*)

This catches most cases but occasionally there will be websites such as:

http://www.xxxx.wordpress.com/hello

which I want to strip to xxxx.wordpress.com.

How can I identify those cases while still identifying all other normal entries?

Answer 1

You expression seems to be working perfectly fine and it outputs what you might want to. I only added an i flag and slightly modify it to:

(https?:\/\/)?([w]{3}\.)?(\w*.\w*)([\/\w]*)

RegEx

If this wasn't your desired expression, you can modify/change your expressions in regex101.com.

RegEx Circuit

You can also visualize your expressions in jex.im:

Python Code

# coding=utf8
# the above tag defines encoding for this document and is for Python 2.x compatibility

import re

regex = r"(https?:\/\/)?([w]{3}\.)?(\w*.\w*)([\/\w]*)"

test_str = ("https://www.facebook.org/hello\n"
    "http://www.xxxx.wordpress.com/hello\n"
    "http://www.xxxx.yyy.zzz.wordpress.com/hello")

subst = "\\3"

# You can manually specify the number of replacements by changing the 4th argument
result = re.sub(regex, subst, test_str, 0, re.MULTILINE | re.IGNORECASE)

if result:
    print (result)

# Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.

JavaScript Demo

const regex = /(https?:\/\/)?([w]{3}\.)?(\w*.\w*)([\/\w]*)/gmi;
const str = `https://www.facebook.org/hello
http://www.xxxx.wordpress.com/hello
http://www.xxxx.yyy.zzz.wordpress.com/hello`;
const subst = `$3`;

// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);

console.log('Substitution result: ', result);