Lex Program to check valid email

Lex is a computer program that generates lexical analyzers. Lex reads an input stream specifying the lexical analyzer and outputs source code implementing the lexer in the C programming language.

The commands for executing the lex program are:

lex abc.l (abc is the file name)
cc lex.yy.c -efl
./a.out

Let’s see lex program to check valid email.

Examples:

Input : 
csetanmayjain@gmail.com
Output :
 Valid

Input : 
!23@43.com
Output : 
Not Valid

Below is the implementation:

/*lex code to accept a  valid email */
%
{
  int flag = 0; %
} %
% [a - z.0 - 9 _] + @[a - z] + ".com" | ".in"
flag = 1; %
%
main() {
  yylex();
  if (flag == 1)
    printf("Accepted");
  else
    printf("Not Accepted");
}

Output:

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