In which encoding the name of fName.log is encoded in both windows and linux?
The encoding used for a file and the encoding use for the name of that file are different things. They don't correlate.
The encoding use for the name of the file is depended on the filesystem. For windows reasonable to expect NTFS and another question (What encoding are filenames in NTFS stored as?) has some information about. For Linux it would be harder to answer and it seems like it also matter what kind of framework is trying to read a file if you look at the answers for a question like: What charset encoding is used for filenames and paths on Linux?