Dear Rene and Philippe,
Thanks for the informative explanation.
Zaldy
> Hi Zaldy,
>
> A short answer to your question(s)
>
> TTree has a pointer to the file where the Tree must be written.
> When calling TTree::Fill, the function will automatically write
> the buffers to the file where the tree was created.
> At the end of your job, if you call tree->AutoSave, the Tree header
> will also be written to the right file. You do not need to do,
> file->cd();
> tree->Write();
> although you may want to do it if you want to write the tree header
> to another file.
>
> Rene Brun
>
> On Sun,
> 20
> Jul 2003, zaldy wrote:
>
> >
> > Dear ROOT Users,
> >
> >
> > In using the methods tree_ptr->Write() and file_ptr->Write(), how does the
> > TTree object communicates with the TFile object?
> >
> > For instance in writing a root file, I noticed the ff. steps from the
> > tutorial(filename: tree*.C) or manual (Users Man. 3.05, pp.212-214):
> >
> > 1. a declaration of the form
> > TFile * firstFILEinput = new TFile("INPUT.root",MODE);
> > TTree * myTree= new TTree("T","Oak Tree");
> >
> > 2. Creating branches;
> > myTree->Branch(.......arguments.......);
> > .......
> >
> > 3. Filling the branches with data;
> > branchName = data_one;
> > .............
> > myTree->Fill();
> >
> > 4. actual writing;
> > myTree->Write();
> > (sometimes: fileOUT->Write(); )
> >
> > Now what about if one has to create another TFile object
> >
> > TFile * anotherFileOUTPUT = new TFile("OUTPUT.root",MODE),
> >
> > how will the TTree select which TFile's to direct?
> > (Or, how intelligent this tree is to choose w/c from the two files to
> > write?)
> >
> > I did not see an explicit
> > declaration on the part of TTree that it has to write to a specific file.
> > So far in the manual, we are told that it is for writing or reading
> > through its MODE.
> >
> > In otherwords, is it INPUT.root or UTPUT.root ?
> > Are we assured that it will not overwrite, for instance, the file
> > "INPUT.root" with mode=>READ?
> >
> > My apology for the many questions.
> >
> > Thanks.
> >
> >
>
--
--------------------------------------------------------
Zaldy A. Nawang
PS Users Room 2
Yon Gokan,
E362, Neutrino Group,
IPNS, KEK,
Japan
e-mail: zaldy@neutrino.kek.jp
Tel. No. : (81) 029864 - 5387
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