SQL & PL/SQL

Hi, I need some help with a simple task.
I am running every night this script:

spool c:\DS01\datalog.txt;
SELECT * FROM EPTABLA_01;
spool off;

easy one, right?
The problem is, I don't want the file to be replaced each time I execute the query, I just want to the data of every night in the same txt. I am trying it with "save append" command, but it just write the query itself and not the content of the table.

So the question is, how do I save the content of the table in a file without deleting the previous content that this file is holding?
help please