To validate characters using Lex > Lex and Yacc Program

To validate characters using Lex > Lex and Yacc Program 

System Programming and Compiler Construction

Program:

%{
/* To validate characters using lex*/
%}
%%
[\t]+                                    ;

[0-9]+                                {printf("This is a valid number\n");}
int|char|float|if|else       {printf("%s- is a keyword \n",yytext);}
[a-zA-Z]+                          {printf("%s- is a character\n",yytext);}
"++"|"--"|"=="|[-+*/]     {printf("%s- is an operator\n",yytext);}
[(){}.;"=]                            {printf("%s- is a special symbol\n",yytext);}
.                                           ECHO;
%%
main()
{
  yylex();
}
int yywrap()
{    
  return(1);
}

OUTPUT:

[root@localhost Desktop]# lex 38spcc2.l
[root@localhost Desktop]# gcc lex.yy.c
[root@localhost Desktop]# ./a.out
int a=10;
int- is a keyword
 a- is a character
=- is a special symbol
This is a valid number
;- is a special symbol

char b;float a=90;
char- is a keyword
 b- is a character
;- is a special symbol
float- is a keyword
 a- is a character
=- is a special symbol
This is a valid number
;- is a special symbol