I have writting a simple script (based on documentation example)
which create a ROOT file with an histogram (class TH1F) in it.
Then it read this file, find a TKey and draw thestogram.
1/ When executing this script in root with script processor:
root  .x test.C
-> Error, a default canvas is displaying but not the histogram.
2/ When executing exacly same commands in root command line:
-> No error, a default canvas id displaying with the histogram.
//Create a pointer to an histograme TH1F *h = new TH1F("histo1","histogram",100,-4,4); // Fill it h->FillRandom("gaus",1000); // open a file and write the Array to the file TFile f("$HOME/Root/files/demo.root","recreate"); h->Write(); f.GetListOfKeys()->Print(); TH1F *h = (TH1F*)f.Get("histo1"); // Draw the histogram h->Draw();