void setup() {
  String[] isbn = loadStrings("../listeIsbn.txt"); //  *listeIsbn.txt* contain 3 lines

  for(int i=0 ; i< isbn.length ; i++){
  output = createWriter("export.txt") ;  // only one line in the .txt export
  output.println(isbn[i]) ;
  output.flush();
  output.close();
}
}