How to validate an IP address using ReGex

Last Updated : 15 Feb, 2023

Given an IP address, the task is to validate this IP address with the help of Regex (Regular Expression) in C++ as a valid IPv4 address or IPv6 address. If the IP address is not valid then print an invalid IP address.

Examples:

Input: str = "203.120.223.13"
Output: Valid IPv4

Input: str = "000.12.234.23.23"
Output: Invalid IP

Input: str = "2F33:12a0:3Ea0:0302"
Output: Invalid IP

Input: str = "I.Am.not.an.ip"
Output: Invalid IP

Approach:

Regex (Regular Expression) In C++ will be used to check the IP address.
Range Specifications
Specifying a range of characters or literals is one of the simplest criteria used in a regex.

i) [a-z] ii) [A-Za-z0-9]

In the above expression ([]) square brackets are used to specify the range.
The first expression will match exactly one lowercase character.
The second expression specifies the range containing one single uppercase character, one lowercase character, and a digit from 0 to 9.
Now to include a '.' as part of an expression, we need to escape '.' and this can be done as :

[\\.0-9]

The above expression indicates an '.' and a digit in the range 0 to 9 as a regex.

regex_match() function is used to match the given pattern. This function returns true if the given expression matches the string. Otherwise, the function returns false.

Here is the implementation of the above approach.

C++

// C++ program to validate // IP address using Regex  #include <bits/stdc++.h> using namespace std;  // Function for Validating IP string Validate_It(string IP) {      // Regex expression for validating IPv4     regex ipv4("(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])");      // Regex expression for validating IPv6     regex ipv6("((([0-9a-fA-F]){1,4})\\:){7}([0-9a-fA-F]){1,4}");      // Checking if it is a valid IPv4 addresses     if (regex_match(IP, ipv4))         return "Valid IPv4";      // Checking if it is a valid IPv6 addresses     else if (regex_match(IP, ipv6))         return "Valid IPv6";      // Return Invalid     return "Invalid IP"; }  // Driver Code int main() {     // IP addresses to validate     string IP = "257.120.223.13";     cout << Validate_It(IP) << endl;      IP = "fffe:3465:efab:23fe:2235:6565:aaab:0001";     cout << Validate_It(IP) << endl;      IP = "2F33:12a0:3Ea0:0302";     cout << Validate_It(IP) << endl;      return 0; }

Java

// Java program to validate // IP address using Regex import java.util.regex.*;  class GFG {    // Function for Validating IP   static String Validate_It(String IP)   {      // Regex expression for validating IPv4     String regex="(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])";      // Regex expression for validating IPv6     String regex1="((([0-9a-fA-F]){1,4})\\:){7}([0-9a-fA-F]){1,4}";      Pattern p = Pattern.compile(regex);     Pattern p1 = Pattern.compile(regex1);      // Checking if it is a valid IPv4 addresses     if (p.matcher(IP).matches())       return "Valid IPv4";      // Checking if it is a valid IPv6 addresses     else if (p1.matcher(IP).matches())       return "Valid IPv6";      // Return Invalid     return "Invalid IP";   }    // Driver Code   public static void main(String args[])   {     // IP addresses to validate     String IP = "257.120.223.13";     System.out.println(Validate_It(IP));      IP = "fffe:3465:efab:23fe:2235:6565:aaab:0001";     System.out.println(Validate_It(IP));      IP = "2F33:12a0:3Ea0:0302";     System.out.println(Validate_It(IP));    } }  // This code is contributed by Aman Kumar.

Python3

# Python3 program to validate # IP address using Regex import re  # Function for Validating IP   def Validate_It(IP):      # Regex expression for validating IPv4     regex = "^((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])$"      # Regex expression for validating IPv6     regex1 = "((([0-9a-fA-F]){1,4})\\:){7}"\              "([0-9a-fA-F]){1,4}"      p = re.compile(regex)     p1 = re.compile(regex1)      # Checking if it is a valid IPv4 addresses     if (re.search(p, IP)):         return "Valid IPv4"      # Checking if it is a valid IPv6 addresses     elif (re.search(p1, IP)):         return "Valid IPv6"      # Return Invalid     return "Invalid IP"  # Driver Code   # IP addresses to validate IP = "257.120.223.13" print(Validate_It(IP))  IP = "fffe:3465:efab:23fe:2235:6565:aaab:0001" print(Validate_It(IP))  IP = "2F33:12a0:3Ea0:0302" print(Validate_It(IP))  # This code is contributed by avanitrachhadiya2155

// C# program to validate // IP address using Regex using System; using System.Text.RegularExpressions;  class GFG {  // Function for Validating IP static string Validate_It(string IP) {      // Regex expression for validating IPv4     string regex="(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])";      // Regex expression for validating IPv6     string regex1="((([0-9a-fA-F]){1,4})\\:){7}([0-9a-fA-F]){1,4}";      Regex p = new Regex(regex);     Regex p1 = new Regex(regex1);      // Checking if it is a valid IPv4 addresses     if (p.IsMatch(IP))     return "Valid IPv4";      // Checking if it is a valid IPv6 addresses     else if (p1.IsMatch(IP))     return "Valid IPv6";      // Return Invalid     return "Invalid IP"; }  // Driver Code public static void Main() {     // IP addresses to validate     string IP = "257.120.223.13";     Console.WriteLine(Validate_It(IP));      IP = "fffe:3465:efab:23fe:2235:6565:aaab:0001";     Console.WriteLine(Validate_It(IP));      IP = "2F33:12a0:3Ea0:0302";     Console.WriteLine(Validate_It(IP));  } }  // This code is contributed by Pushpesh Raj.

JavaScript

// JavaScript program to validate // IP address using Regex  // Function for Validating IP function Validate_It(IP) {      // Regex expression for validating IPv4     let ipv4 = /(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])/;      // Regex expression for validating IPv6     let ipv6 = /((([0-9a-fA-F]){1,4})\:){7}([0-9a-fA-F]){1,4}/;      // Checking if it is a valid IPv4 addresses     if (IP.match(ipv4))         return "Valid IPv4";      // Checking if it is a valid IPv6 addresses     else if (IP.match(ipv6))         return "Valid IPv6";      // Return Invalid     return "Invalid IP"; }  // Driver Code function main() {     // IP addresses to validate     let IP = "257.120.223.13";     console.log(Validate_It(IP));      IP = "fffe:3465:efab:23fe:2235:6565:aaab:0001";     console.log(Validate_It(IP));      IP = "2F33:12a0:3Ea0:0302";     console.log(Validate_It(IP)); }  main();  // This code is contributed by akashish__

Output

Invalid IP Valid IPv6 Invalid IP

Time Complexity: O (N)
Auxiliary Space: O (1)

How to validate an IP address using ReGex

abhishek_padghan

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How to validate an IP address using ReGex

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