[ROOT] Writing TTree changes on a file

From: Anton Fokin (anton.fokin@smartquant.com)
Date: Mon Feb 26 2001 - 01:34:27 MET


Hi Rene and rooters,

I am a bit lost with TTrees and TFile. What I want to do is quite simple.
Assume I have a root file with a root tree and I want to open the file and
add several entries in the tree.

TFile *File = new TFile("trade.data", "update");
TTree *Tree = (TTree*) TFile->Get("IBM"); ...
. ... Tree->Fill();
TTree->Write();
TFile->Close();

does the job but it writes a copy of the whole tree with only several new
entries added. I can do TFile->Purge(); of course but it is not what I want
to do. I want to make my trees on file and in memory identical, i.e. add
several new entries to the same tree on disk without writing a new copy of
the tree!

Regards,
Anton

http://www.smartquant.com



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