Duplicate file descriptor with its own file offset

Question

How can one create a new file descriptor from an existing file descriptor such that the new descriptor does not share the same internal file structure/entry in the file table? S

Answer 1

Why don't you just open the file a second time with open() or CreateFile() on windows? This gives you all freedom of different access rights and separate offset.

This of course has the drawback that you you can not open the file exclusively, but it solves your problem very simply.