Calling directory file

I don’t understand why the following code has a bug. In the cout I see correctly Event001,Event002, Event003 etc etc but I get “Unknown directory Event001”, “Unknown directory Event002” “Unknown directory Event003” etc etc

    sprintf(c, "%03d", j);
    TString stringa = "Event"+ string(c);
    TDirectoryFile *hpx = new TDirectoryFile(stringa,"");
    cout << stringa << " ." << endl;


please look up the TDirectoryFile constructor ( It takes a pointer to the mother directory as 4th argument and defaults to 0 (i.e. no mother directory) if it isn’t explicitly given. You want your directories to be below hfile, so that’s their mother directory.

 TDirectoryFile *hpx = new TDirectoryFile(stringa,"", "", hfile);

ok thanks!