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Reading or writing files within ROOT requires the class TXNetFile which is found in the library libNetx.so.
This library is loaded automatically if the static method TFlle::Open() is used to open the file.

root \[2\] TFile \*f = TFile::Open("root://glast-rdr//wilko/test/basic.root")     // Reading a file

If  TXnetFile is used directly the library has to be loaded first:

  

 

   root\[2\]  .L $ROOTSYS/libNetx.so

       root\[3\]  TFile \*f = new TXNetFile("root://glast-rdr//wilko/test/basic.root", ,"RECREATE"))    // Open a file for writing

TChain will also automatically use TXNetFile if the root files are specified using the "root://<xrootdSrv>/..."  names.
The next example will chain three root files and read them from xrootd:

&nbsp;&nbsp;&nbsp; &nbsp;&nbsp; root\[1\]&nbsp; TChain \*ch = new TChain(<TreeName>)

&nbsp;&nbsp;&nbsp; &nbsp;&nbsp; root\[2\]&nbsp; ch->Add("root://<xrootdSrv>//test/testtree1.root)

&nbsp;&nbsp;&nbsp; &nbsp;&nbsp; root\[3\]&nbsp; ch->Add("root://<xrootdSrv>//test/testtree2.root)

&nbsp;&nbsp;&nbsp;&nbsp; &nbsp; root\[4\]&nbsp; ch->Add("root://<xrootdSrv>//test/testtree3.root)

Using Xrootd client command line tools

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