Expand description
dup3(fd, new, flags)—Creates a new OwnedFd instance that shares the
same underlying file description as the existing OwnedFd instance,
closing new and reusing its file descriptor, with flags.
dup3 is the same as dup2 but adds an additional flags operand,
and it fails in the case that fd and new have the same file descriptor
value. This additional difference is the reason this function isn’t named
dup2_with.