It is working … simply the messages that you see come from stdout (i.e. 1), not from stderr (i.e. 2).
You can get rid of the canvas related message if you add into your “toto.C” something like (somewhere before the first “draw” command):
new TCanvas(“c1”, “c1”);
You can get rid of the “processing” message if you run your macro using:
echo ‘gROOT->LoadMacro(“toto.C”); toto(); gSystem->Exit(0);’ | root -b -l
See also [url]Compile and run from command prompt