How to validate MAC address using Regular Expression

Given string str, the task is to check whether the given string is a valid MAC address or not by using Regular Expression.

A valid MAC address must satisfy the following conditions: 

1. It must contain 12 hexadecimal digits.
2. One way to represent them is to form six pairs of the characters separated with a hyphen (-) or colon(:). For example, 01-23-45-67-89-AB is a valid MAC address.
3. Another way to represent them is to form three groups of four hexadecimal digits separated by dots(.). For example, 0123.4567.89AB is a valid MAC address.

Examples:

Input: str = “01-23-45-67-89-AB”; 
Output: true 
Explanation:
The given string satisfies all the above mentioned conditions. Therefore, it is a valid MAC address.

Input: str = “01-23-45-67-89-AH”; 
Output: false 
Explanation:
The given string contains ‘H’, the valid hexadecimal digits should be followed by letter from a-f, A-F, and 0-9. Therefore, it is not a valid MAC address.

Input: str = “01-23-45-67-AH”; 
Output: false 
Explanation:
The given string has five groups of two hexadecimal digits. Therefore, it is not a valid MAC address. 

Approach: The idea is to use Regular Expression to solve this problem. The following steps can be followed to compute the answer. 

• Get the String.
• Create a regular expression to check valid MAC address as mentioned below:

regex = “^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})|([0-9a-fA-F]{4}\\.[0-9a-fA-F]{4}\\.[0-9a-fA-F]{4})$”; 

• Where: 
  • ^ represents the starting of the string.
  • ([0-9A-Fa-f]{2}[:-]){5} represents the five groups of two hexadecimal digits separated by hyphens (-) or colons (:)
  • ([0-9A-Fa-f]{2}) represents the one groups of two hexadecimal digits.
  • | represents the or.
  • ( represents the starting of the group.
  • [0-9a-fA-F]{4}\\. represents the first part of four hexadecimal digits separated by dots (.).
  • [0-9a-fA-F]{4}\\. represents the second part of four hexadecimal digits separated by dots (.).
  • [0-9a-fA-F]{4} represents the third part of four hexadecimal digits.
  • ) represents the ending of the group.
  • $ represents the ending of the string.
• Match the given string with the Regular Expression. In Java, this can be done by using Pattern.matcher().
• Return true if the string matches with the given regular expression, else return false.

Below is the implementation of the above approach:

C++

// C++ program to validate the
// MAC address
// using Regular Expression
#include <iostream>
#include <regex>
using namespace std;

// Function to validate the MAC address
bool isValidMACAddress(string str)
{

    // Regex to check valid MAC address
    const regex pattern(
    "^([0-9A-Fa-f]{2}[:-]){5}"
      "([0-9A-Fa-f]{2})|([0-9a-"
    "fA-F]{4}\\.[0-9a-fA-F]"
      "{4}\\.[0-9a-fA-F]{4})$");

    // If the MAC address
    // is empty return false
    if (str.empty())
    {
        return false;
    }

    // Return true if the MAC address
    // matched the ReGex
    if (regex_match(str, pattern))
    {
        return true;
    }
    else
    {
        return false;
    }
}

// Driver Code
int main()
{
    // Test Case 1:
    string str1 = "01-23-45-67-89-AB";
    cout << isValidMACAddress(str1) << endl;

    // Test Case 2:
    string str2 = "01:23:45:67:89:AB";
    cout << isValidMACAddress(str2) << endl;

    // Test Case 3:
    string str3 = "0123.4567.89AB";
    cout << isValidMACAddress(str3) << endl;

    // Test Case 4:
    string str4 = "01-23-45-67-89-AH";
    cout << isValidMACAddress(str4) << endl;

    // Test Case 5:
    string str5 = "01-23-45-67-AH";
    cout << isValidMACAddress(str5) << endl;

    return 0;
}

// This code is contributed by yuvraj_chandra

Java

// Java program to validate
// MAC address using
// regular expression

import java.util.regex.*;
class GFG {

    // Function to validate
    // MAC address
    // using regular expression
    public static boolean isValidMACAddress(String str)
    {
        // Regex to check valid
        // MAC address
        String regex = "^([0-9A-Fa-f]{2}[:-])"
                       + "{5}([0-9A-Fa-f]{2})|"
                       + "([0-9a-fA-F]{4}\\."
                       + "[0-9a-fA-F]{4}\\."
                       + "[0-9a-fA-F]{4})$";

        // Compile the ReGex
        Pattern p = Pattern.compile(regex);

        // If the string is empty
        // return false
        if (str == null)
        {
            return false;
        }

        // Find match between given string
        // and regular expression
        // uSing Pattern.matcher()

        Matcher m = p.matcher(str);

        // Return if the string
        // matched the ReGex
        return m.matches();
    }

    // Driver code
    public static void main(String args[])
    {

        // Test Case 1:
        String str1 = "01-23-45-67-89-AB";
        System.out.println(isValidMACAddress(str1));

        // Test Case 2:
        String str2 = "01:23:45:67:89:AB";
        System.out.println(isValidMACAddress(str2));

        // Test Case 3:
        String str3 = "0123.4567.89AB";
        System.out.println(isValidMACAddress(str3));

        // Test Case 4:
        String str4 = "01-23-45-67-89-AH";
        System.out.println(isValidMACAddress(str4));

        // Test Case 5:
        String str5 = "01-23-45-67-AH";
        System.out.println(isValidMACAddress(str5));
    }
}

Python3

# Python3 program to validate
# MAC address using
# using regular expression
import re

# Function to validate MAC address.


def isValidMACAddress(str):

    # Regex to check valid
    # MAC address
    regex = ("^([0-9A-Fa-f]{2}[:-])" +
             "{5}([0-9A-Fa-f]{2})|" +
             "([0-9a-fA-F]{4}\\." +
             "[0-9a-fA-F]{4}\\." +
             "[0-9a-fA-F]{4})$")

    # Compile the ReGex
    p = re.compile(regex)

    # If the string is empty
    # return false
    if (str == None):
        return False

    # Return if the string
    # matched the ReGex
    if(re.search(p, str)):
        return True
    else:
        return False

# Driver code


# Test Case 1:
str1 = "01-23-45-67-89-AB"
print(isValidMACAddress(str1))

# Test Case 2:
str2 = "01:23:45:67:89:AB"
print(isValidMACAddress(str2))

# Test Case 3:
str3 = "0123.4567.89AB"
print(isValidMACAddress(str3))

# Test Case 4:
str4 = "01-23-45-67-89-AH"
print(isValidMACAddress(str4))

# Test Case 5:
str5 = "01-23-45-67-AH"
print(isValidMACAddress(str5))

# This code is contributed by avanitrachhadiya2155

C#

// C# program to validate
// MAC address using
// regular expression

using System;
using System.Text.RegularExpressions;

class GFG {

    // Function to validate
    // MAC address
    // using regular expression
    public static bool isValidMACAddress(string str)
    {
        // Regex to check valid
        // MAC address
        string regex = "^([0-9A-Fa-f]{2}[:-])"
                    + "{5}([0-9A-Fa-f]{2})|"
                    + "([0-9a-fA-F]{4}\\."
                    + "[0-9a-fA-F]{4}\\."
                    + "[0-9a-fA-F]{4})$";

        // Compile the ReGex
        Regex p = new Regex(regex);

        // If the string is empty
        // return false
        if (str == null)
        {
            return false;
        }

        // Find match between given string
        // and regular expression
        // uSing Pattern.matcher()

        Match m = p.Match(str);

        // Return if the string
        // matched the ReGex
        return m.Success;
    }

    // Driver code
    public static void Main()
    {

        // Test Case 1:
        string str1 = "01-23-45-67-89-AB";
        Console.WriteLine(isValidMACAddress(str1));

        // Test Case 2:
        string str2 = "01:23:45:67:89:AB";
        Console.WriteLine(isValidMACAddress(str2));

        // Test Case 3:
        string str3 = "0123.4567.89AB";
        Console.WriteLine(isValidMACAddress(str3));

        // Test Case 4:
        string str4 = "01-23-45-67-89-AH";
        Console.WriteLine(isValidMACAddress(str4));

        // Test Case 5:
        string str5 = "01-23-45-67-AH";
        Console.WriteLine(isValidMACAddress(str5));
    }
}

// This code is contributed by Aman Kumar.

Javascript

// Javascript program to validate
// MAC Address  using Regular Expression

// Function to validate the
// MAC_Address
function isValidMACAddress(str) {
    // Regex to check valid
    // MAC_Address
    let regex = new RegExp(/^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})|([0-9a-fA-F]{4}.[0-9a-fA-F]{4}.[0-9a-fA-F]{4})$/);

    // if str
    // is empty return false
    if (str == null) {
        return "false";
    }

    // Return true if the str
    // matched the ReGex
    if (regex.test(str) == true) {
        return "true";
    }
    else {
        return "false";
    }
}

// Driver Code
// Test Case 1:
let str1 = "01-23-45-67-89-AB";
console.log(isValidMACAddress(str1));

// Test Case 2:
let str2 = "01:23:45:67:89:AB";
console.log(isValidMACAddress(str2));

// Test Case 3:
let str3 = "0123.4567.89AB";
console.log(isValidMACAddress(str3));

// Test Case 4:
let str4 = "01-23-45-67-89-AH";
console.log(isValidMACAddress(str4));

// Test Case 5:
let str5 = "01-23-45-67-AH";
console.log(isValidMACAddress(str5));

// This code is contributed by Rahul Chauhan

Output

true
true
true
false
false

Time Complexity: O(N) for each testcase, where N is the length of the given string. 
Auxiliary Space: O(1)