Get the directory of a TFile - Copy a root file from a directory to another directory

[atha.stam]

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ROOT Version: 6.18/04
Platform: Ubuntu 18.04
Compiler: gcc 7.5.0 (Ubuntu 7.5.0-3)

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Dear co-rooters,

I’m trying to open a root file and add a TBranch to it. Since I want to keep the original file, I thought of copying it and open the clone with the UPDATE option.

I tried copying the file by piping in bash and using cp command. If the file lives in another directory (i.e. I execute the macro by add_branch("../raw_data/run1.root") I get the following error

cp: cannot create regular file 'new_../raw_data/run1.root': No such file or directory
SysError in <TFile::TFile>: file new_../raw_data/run1.root can not be opened (No such file or directory)

I understand why I get this error and I know that if I add a suffix in the new file name instead of a prefix it will work. A snippet of my code is

void add_branch(TString filename_in){

    // (a) Open the file
    TFile *f_root = TFile::Open(filename_in, "READ");
    
    // copy the file with cp command
    TString new_filename_in = TString::Format("new_%s", filename_in.Data());
    gSystem->Exec( TString::Format("cp %s new_%s", filename_in.Data(), filename_in.Data()) );
    f_root->Close();
    f_root = TFile::Open(new_filename_in, "UPDATE");

}

I also tried using the TFile::Cp() function but if the file lives in another directory things get complicated again because I get an error for the similar reasons.

[TFile::Cp] Total 1292.43 MB	|====================| 100.00 % [1104.8 MB/s]
SysError in <TFile::TFile>: file new_files/../raw_data/run1.root can not be opened (Not a directory)

This is a snippet of the code I’m using.

void add_branch(TString filename_in){

    // (a) Open the file
    TFile *f_root = TFile::Open(filename_in, "READ");

    //create a directory because Cp() wants it
    gSystem->Exec("mkdir new_files");
 
    // copy the file in a directory using Cp() function
    f_root->Cp("new_files");
    f_root->Close();
    f_root = TFile::Open(TString::Format("new_files/%s", filename_in.Data()), "UPDATE");
}

What I need is to get the directory of the root file I’m opening but when I’m calling gDirectory->pwd() I also get the filename i.e.

../raw_data/run1.root:/

Is there a way to get only the directory of the root file or does anyone have any idea on to copy the file?

[vpadulan]

Hi @atha.stam,
It’s easier for you to just cp the root file over to the new folder directly from your command line and then proceed with the modifications.

gDirectory->pwd() returns the path to the current TDirectory object, which does not correspond to the file system’s folder you are currently working in.

@atha.stam

f_root->Cp("new_files");

Have you tried to give it also the file name as in "new_files/run1.root" ?

[atha.stam]

Copying from the command line is an option but since this is supposed to be a macro to be used by people that want just to run a macro, I thought to make it as simple as possible.

I indeed tried to use Cp(new_file/filename.root")` but I got the same issue.