Lazarus/Delphi – writing to text file without overwriting next time

I’m using Lazarus and I wanted to save information to a text when the program terminates. But each time I reopen the program it overwrites what was there before in the text file. It would be OK to append a new line to the file or even create a different text file each time. This is what I have:

var
  // … other variable declarations omitted …
  s: TStringList;
begin
  s:= TStringList.Create;
  s.Add(datetostr(now));
  s.SaveToFile(datetostr(now)+'.txt');
  s.Free;

But it gives me an error.

All you need to do is open your file in append mode, and then add your text. It will put the new data at the end of the file:

  AssignFile(tfOut, C_FNAME);

  try
    // Open for append, write and close.
    append(tfOut);

    writeln(tfOut, 'New data for text file');
    writeln(tfOut, 'New informtion should be at the end of the file.');

    CloseFile(tfOut);

  except
    on E: EInOutError do
     writeln('File error. Elaboration: ', E.Message);
  end;