void drawhistcustom() {
   TCanvas *c = new TCanvas("c","custom option to draw an histogram",700,500);
   TH1F *h = new TH1F("h", "h", 100, -5, 5);
   h->FillRandom("gaus", 10000);
   TExec *ex = new TExec("ex","DrawBin();");
   h->GetListOfFunctions()->Add(ex);
   h->Draw("P");
}


void DrawBin()
{
   TLine *l;
   TH1F *h = (TH1F*)gPad->GetListOfPrimitives()->FindObject("h");
   int n = h->GetNbinsX();
   Double_t x1,x2,y;
   for (int i=1; i<=n; i++) {
      y = h->GetBinContent(i);
      x1= h->GetBinLowEdge(i);
      x2 = h->GetBinWidth(i)+x1;
      l= new TLine(x1,y,x2,y);
      l->Paint();
   }
}