void testpost()
{

  ps = new TPostScript("file.ps",121);

  h=new TH1F("h1","h1",100,-3,3);
  h->FillRandom("gaus",10000);

  c = new TCanvas("blah","blah");
  h->Draw();
  c->Update();

  h->FillRandom("gaus",10000);
  h->Draw();
  c->Update();

  //  ps->NewPage();
  c = new TCanvas("blubb","blubb");
  h->FillRandom("gaus",10000);
  h->Draw();
  c->Update();

  ps->Close();

  gSystem->Exec("gv file.ps&");

}