Regex for IPv4 CIDR Notation

javascript

const regex = /^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\/([0-9]|[12][0-9]|3[0-2])$/;
const isValid = regex.test(value);

python

import re
pattern = r'^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\/([0-9]|[12][0-9]|3[0-2])$'
if re.match(pattern, value):
    print("valid")

ruby

pattern = /^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\/([0-9]|[12][0-9]|3[0-2])$/
if value =~ pattern
  puts "valid"
end

php

if (preg_match('/^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\/([0-9]|[12][0-9]|3[0-2])$/', $value)) {
    echo "valid";
}

java

String pattern = "^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\/([0-9]|[12][0-9]|3[0-2])$";
boolean isValid = value.matches(pattern);