RegEx-validate IP address. Defined below is the pattern for checking an IP address with value: String Pattern Explanation

Transcription

1 RegEx-validate IP address Defined below is the pattern for checking an IP address with value: String Pattern Explanation 240 ^[0-9]1,3 To define the starting part as number ranging from 1 digit to 3 digits. \. To define a dot 30 [0-9]1,3 To define a number ranging from 1 digit to 3 digits. \. To define a dot 20 [0-9]1,3 To define a number ranging from 1 digit to 3 digits. \. To define a dot 60 [0-9]1,3 To define a number ranging from 1 digit to 3 digits

2 $ To define an ending boundary for the number. So the final regex pattern to match with an IP address should be as ^[0-9]1,3\.[0-9]1,3\.[0-9]1,3\.[0-9]1,3$ Sample code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Regex_FirstExample class Program static void Main(string[] args) string number = " "; // number to check string pattern // pattern to check System.Console.WriteLine("The number is : " + number);

3 System.Console.WriteLine("The pattern string is : " + pattern); if (System.Text.RegularExpressions.Regex.IsMatch(number, pattern)) // regex to validate the number System.Console.WriteLine(" The given number is a valid pattern"); else System.Console.WriteLine(" The given number is an invalid pattern"); // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey();

4 Code Explanation: The libraries are imported by default in C# class file.

5 using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; Here System is the parent library for C# code. Collections.Generic allow to generate strongly typed collections for better performance. The System.Text namespace is a holder for classes to represent ASCII and Unicode character encodings. RegularExpressions class is a child class of System.Text namesapce. The code namespace Regex_FirstExample defines a holder to contain one or more class. Here it contains a class named Program. The line of code static void Main(string[] args) defines a static method called Main, whose elements can be called without an instance. It contains a string array as parameter, to receive input from the console window. The lines of code below declare two string variables, one with a string of numbers for IP address and other with a string pattern to match an IP pattern as follows: string number = " "; // number to check string pattern

6 Now the pattern string is checked against the string of numbers and if the check satisfies, a message is shown at the console as The given number is a valid pattern else The given number is an invalid pattern. This is done by the following lines of code: if (System.Text.RegularExpressions.Regex.IsMatch(number, pattern)) // regex to validate the number System.Console.WriteLine(" The given number is a valid pattern"); else System.Console.WriteLine(" The given number is an invalid pattern"); The pattern can be rewritten as shown below for the IP Address verification: string number = " "; // number to check string pattern // pattern to check

7 String Pattern Explanation 240 (\d1,3\.) To define a number ranging from 1 digit to 3 digits followed by a dot 60 [0-9]1,3$ To define a number ranging from 1 digit to 3 digits as the ending boundary for the number. Output: The string pattern "(\d1,3\.)3[0-9]1,3$" checks whether the string contains digits as denoted by \d digits range from 1 to 3 counts as denoted by 1,3 pattern digits are followed by a. as informed by \. pattern and boundary entry is a digit between 0 to 9, with a count of 1 to 3 digits as denoted by [0-9]1,3$

8 Since the condition is satisfied with the input number, the output is received as The given number is a valid pattern.