TString dir = gROOT->GetTutorialDir();

TFITSHDU hdu(dir + "/fitsio/sample4.fits[1]");

const auto nColumns = hdu.GetTabNColumns();
printf("The table has %d columns:\n", nColumns);
for (auto i : ROOT::TSeqI(nColumns)) {
   printf(" - Column %d: %s\n", i, hdu.GetColumnName(i).Data());
}

gROOT->GetListOfCanvases()->Draw()