FLEX program writing one too many "\n" on output file

Question

The last token of each line from the "example.y" file is written with an extra "\n". We also found out that, if we get the string length of the buffer, when it contains the element of the last token of each line, that length is the size of that token from the array tokensa plus 1.

    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>
    #include <fcntl.h>

    char *tokensa[100];
    int i = 0;

    char *termsa[100];
    int j = 0;
%}

%option stack
%x tokens termos termo

Tokens    ^\%token
Token     [a-zA-Z]+
Termos    [ \t]*[a-zA-Z]+[ \t]+\:
Lixo      [ \t]*[a-zA-Z]*[ \t]*['’]
Termo     [^'’]+
Barras    ^[ \t]+\|

%%

{Tokens}                            { BEGIN tokens ; }
<tokens>[ \t]*\n                    { BEGIN INITIAL ; }
<tokens>[^ \n\t]+                   { tokensa[i] = strdup(yytext); i++; }

{Termos}                            { yy_push_state(termos) ; }

<termos>{
    {Lixo}                          { yy_push_state(termo) ; }
    ([ \t]+\{.*\n)|\n               { yy_pop_state() ; }
}  

<termo>{
    ['’][ \t]?                      { yy_pop_state() ; }
    {Termo}                         { termsa[j] = strdup(yytext); j++; }
}

{Barras}                            { yy_push_state(termos) ; }

<*>(.|\n)                           { ; }

%%

int yywrap()
{ return(1); }

int main()
{   
    char buffer[1024];
    size_t nbytes;
    ssize_t bytes_written;
    int fd;

    yylex();

    fd = open("lexgen.txt", O_WRONLY | O_CREAT | O_TRUNC, 0640);

    write(fd, "%%\n", 3);
    for(int k = 0; k < i; k++){
        strcpy(buffer, tokensa[k]);
        nbytes = strlen(buffer);
        write(fd, "FIXME {return ", 14);
        bytes_written = write(fd, buffer, nbytes);
        write(fd, ";}\n", 3);
        nbytes = 0;
    }
    buffer[0] = '\0';
    write(fd, "[", 1);
    for(int l = 0; l < j; l++){
        strcpy(buffer, termsa[l]);
        nbytes = strlen(buffer);
        write(fd, buffer, nbytes);
    }
    write(fd, "] {return yytext[0];}\n", 22);
    write(fd, "%%", 2);
    close(fd);
    return 0;
}

Expected output:

%%
FIXME {return LISTA;}
FIXME {return NUMERO;}
FIXME {return PALAVRA;}
FIXME {return TESTE;}
[.,] {return yytext[0];}
%%

Obtained output:

%%
FIXME {return LISTA;}
FIXME {return NUMERO;}
FIXME {return PALAVRA
;}
FIXME {return TESTE
;}
[.,] {return yytext[0];}
%%

example.y:

%{
#include <stdio.h>
#include <string.h>

int conta;
%}

%token LISTA NUMERO     PALAVRA
%token TESTE
%%

Lista : LISTA elementos '.'     { printf("comprimento = %d\n", conta) ; }
      ;

elementos : elemento            { conta = 1 ; }
      | elementos ',' elemento  { conta++ ; }
      ;

elemento : NUMERO   | PALAVRA
     ;

%%

#include "lex.yy.c"

int yyerror(char *s){
    printf("Frase inválida: %s\n", s);
}

int main(){
        printf("inicio do parsing\n");
    yyparse();
    return 0;
        printf("fim do parsing\n");

}