Lex program that finds the lenght of longest word

/*Write a Lex program that finds the length of the longest word (defined as a contiguous

 string of upper and lower case letters) in the input.*/

 

%{ 

#include<stdio.h>

int longest_word=0;

%}

%%

[a-zA-Z]+ {

if(yyleng>k)

{  longest_word= yyleng;

}

}

%%

int main()

{

 yyin=fopen("abc.txt","r");

 yylex(); 

 printf("largest: %d",longest_word);

 printf("\n");

 return 0;

}

// abc.txt file

output: