How to write in a text file

ROOT
1

Hi

I have been using something like

[code] tr_x_sec = new TTree(“CrossX”,“CrossX info”);

Double_t x_sec;
tr_x_sec->Branch(“x_sec”,&x_sec,“x_sec/D”);
tr_x_sec->ReadFile(“file.txt”,“x_sec”);
[/code]

in order to read from a text file

How can I write some string / values to a text file and save it as well?

Thanks

2

VIVE L’AMOUR!
try, for example, “ofstream”: http://www.cplusplus.com/reference/iostream/ofstream
Examples: create/open/close a file: http://www.cplusplus.com/reference/iostream/ofstream/ofstream/ and/or http://www.cplusplus.com/reference/iostream/ofstream/open/ and/or http://www.cplusplus.com/reference/iostream/ofstream/close/
Example: write data: http://www.cplusplus.com/reference/iostream/ostream/operator%3C%3C/

Unless what you wanted was just something like:

root […] tr_x_sec->SetScanField(0);
root […] tr_x_sec->Scan("*"); > tr_x_sec.out.txt

See: http://root.cern.ch/root/html/TTree.html#TTree:Scan and http://root.cern.ch/root/html/TTreePlayer.html#TTreePlayer:Scan for details.

However, I don’t know if ROOT is able to parse such a text output afterwards, for example in order to ‘tr_x_sec->ReadFile(“tr_x_sec.out.txt”)’. You might need to edit this file manually. If you have just one “text row” per “tree entry”, remove the first column (called “Row”) and get rid of all “*” characters that are present inside (and possibly modify/add the first line which can keep all branch descriptions - see http://root.cern.ch/root/html/TTree.html#TTree:ReadFile for details).
An expert’s advice is needed here.

I am stupid. No?
Pepe Le Pew.

3

Hi,

You can also redirect the output of Scan as follow:

// Read and dump the tree entries 
t->GetPlayer()->SetScanRedirect(kTRUE); // You may have to cast t.GetPlayer() to a TTreePlayer*
t->GetPlayer()->SetScanFileName("output.txt");
t->Scan("*");

Cheers,
Philippe.

1 Like
4

The method:

((TTreePlayer*)(t->GetPlayer()))->SetScanRedirect(kTRUE);
((TTreePlayer*)(t->GetPlayer()))->SetScanFileName(“output.txt”);
t->Scan("*");

produces the same output text file format as the one in my previous post here.

The question is … can ROOT read it back?
If not, is there any other simple method to “dump” a TTree into an ascii file and read it back later (let’s assume that the TTree is “simple enough”, whatever this “requirement” may mean in the context here)?

5

No. short of writing your own MakeClass/MakeSelector/MakeProxy or TTree::Draw script listing explicitly the variable and the format.

Cheers,
Philippe.

6

where can I find this .txt file then…??? in the root session, I do not have this file…

7

where an I find this .txt file. In the root session, this file is absent…??

8 
root [0] ((TTreePlayer*)(ntuple->GetPlayer()))->SetScanRedirect(kTRUE);
root [1] ((TTreePlayer*)(ntuple->GetPlayer()))->SetScanFileName("output.txt");
root [2] ntuple->Scan();
File <output.txt> created
root [3] .! ls -l output.txt
-rw-r--r--  1 couet  staff  1825292 Sep  3 13:22 output.txt
root [4]
1 Like
9

Thankyou Dear couet…God Bless you…!!