Returns an output stream for overwriting the file in readwrite mode, possibly creating a backup copy of the file first. If the file doesn't exist, it will be created.
gFileReplaceReadwrite(object, etag, make.backup, flags, cancellable = NULL, .errwarn = TRUE)
For details about the behaviour, see
gFileReplace which does the same
thing but returns an output stream only.
Note that in many non-local file cases read and write streams are not
supported, so make sure you really need to do read and write streaming,
rather than just opening for reading or writing.