For sessions running on Linux, a GsFile >> flush may not return nil (implying
that the flush succeed), when the flush did not occur and no bytes were
written to disk. This is the case if the target instance of GsFile is
open on a disk that is full, and cannot be written to.
This is an error in the Linux operating system call fflush().
The GsFile >> close method will error if the disk is full.
Last updated: 11/20/09