Valid Phone number

Steilla Mitchel 614 12 Jun 2024

Given a text file file.txt that contains a list of phone numbers (one per line), write a one-liner bash script to print all valid phone numbers.

You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)

You may also assume each line in the text file must not contain leading or trailing white spaces.

1 Answers

Ravi Vishwakarma 12 Jun 2024

Let's write code to validate the phone number in a specific format using regex in C#.

// Method to validate the phone number
        public static bool IsValidPhoneNumber(string PhoneNumber)
        {
            // Check if the input string is null or empty
            if (string.IsNullOrEmpty(PhoneNumber))
            {
                // Return false if the phone number is null or empty
                return false;
            }

            // Define the regex pattern to match valid phone numbers in the formats
            // (222) 222-2222 and 222-222-2222
            string pattern = @"^\(?\d{3}\)?[- ]?\d{3}[-]\d{4}$";

            // Use Regex.IsMatch to check if the phone number matches the pattern
            // RegexOptions.Multiline is used to ensure the pattern is applied to each line if the input contains multiple lines
            return Regex.IsMatch(PhoneNumber, pattern, RegexOptions.Multiline);
        }

Explanation:

^ asserts the position at the start of the string.
\(? optionally matches an opening parenthesis (.
\d{3} matches exactly three digits.
\)? optionally matches a closing parenthesis ).
[- ]? optionally matches a hyphen - or a space .
\d{3} matches exactly three digits.
[-] matches exactly a hyphen -.
\d{4} matches exactly four digits.
$ asserts the position at the end of the string.

Now call this function

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;
namespace ConsoleApp1
{
    public class Program
    {
        public static void Main()
        {
            IList<string> list = new List<string>
            {
                "(222) 222-2222",
                "222-222-2222",
                "124-125-4585",
                "996 748 8596",
                "7485965874",
                "(222) 222-2222", "222-222-2222", "123 456 7890", "222.222.2222"
            };

			foreach (var item in list)
            {
                bool IsMatch = Program.IsValidPhoneNumber(item);

                Console.BackgroundColor = IsMatch ? ConsoleColor.DarkGreen : ConsoleColor.Red;

                Console.WriteLine(item + " " + IsMatch);
                Console.ResetColor();
            }

            Console.ReadLine();
        }
	}	
}

Output :

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Valid Phone number

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