Ask: how to transfer the parameter for the root scritpt

ROOT
4

Actually, you have three possibilities:

root -l -b -q DrawDiLepPlots.C(3)
root -l -b -q DrawDiLepPlots.C\ (\ 3\ )

root -l -b -q "DrawDiLepPlots.C(3)"
root -l -b -q “DrawDiLepPlots.C ( 3 )”

root -l -b -q 'DrawDiLepPlots.C(3)'
root -l -b -q ‘DrawDiLepPlots.C ( 3 )’

Added: See, for example, ROOT User’s Guide -> Getting Started -> Start and Quit a ROOT Session