Lex Program For checking a valid URL

Problem: Write a Lex program for checking a valid URL.

Explanation:
Lex is a computer utility that generates some lexical analyzers. Lex reads a stream of characters as input specifying the lexical analyzer and give source code as the output implementing the lexer in the C programming language.

Prerequisite: Flex (Fast Lexical Analyzer Generator)

Examples:

Input: geeksforgeeks 
Output: INVALID URL

Input: https://www.geeksforgeeks.org
Output: VALID URL

Implementation:

%% 
((http)|(ftp))s?:\/\/[a-zA-Z0-9]{2, }(\.[a-z]{2, }) 
       +(\/[a-zA-Z0-9+=?]*)* {printf("\nURL Valid\n");} 
  
.+ {printf("\nURL Invalid\n");} 
  
%% 
  
   
// driver program 
void main()  
 { 
    printf("\nEnter URL : "); 
    yylex(); 
    printf("\n"); 
 } 

Output:

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