Demonstrate the use of lex predefined variables (yytext, yyleng, yyin) with the help of program Inputted from text file

%{

#include<stdio.h>

%}

%%

[a-z]* printf("matched string %s and length is %d",yytext,yyleng);

.* printf("%s invalid",yytext);

%%

int yywrap()

{

return 1;

}

main()

{

FILE *fp;

fp=fopen("text.txt","r");

if(fp==NULL)

{

  printf("file not found");

}

yyin=fp;

yylex();

fclose(fp);
}

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