How to build an analysis program based on C++/ROOT

this is a template which can be helpful to make automatically a C++ program for analysis any number of ROOT trees:

Download the file: gntuple.tgz
Unpack the file: tar -zvxf gntuple.tgz.
Copy any number of ROOT files to the directory "ntuple". All files must have exactly the same structure with at least one ROOT tree.
Build the list with root files and the TTree header file as "python make.py".
Make executable: "make". Run the program: "./main".
The program "main" runs over all files and print the total number of processed events. Put your analysis program in "analysis.cxx". The output file with ROOT histograms is "out.root"