How can I tell if a netCDF file uses the classic format or 64-bit offset format?
The short answer is that under most circumstances, you should not care, if you use version 3.6.0 or later of the netCDF library. But the difference is indicated in the first four bytes of the file, which are ‘C’, ‘D’, ‘F’, ‘\001’ for the classic netCDF format and ‘C’, ‘D’, ‘F’, ‘\002’ for the 64-bit offset format. On a Unix system, one way to display the first four bytes of a file, say foo.
