Flushes all buffers associated with a group to disk
herr_t H5Gflush(hid_t group_id)
IN: Identifier of the group to be flushed
H5G_FLUSH causes all buffers associated with a group to be immediately flushed to disk without removing the data from the cache.
HDF5 does not possess full control over buffering. H5G_FLUSH flushes the internal HDF5 buffers and then asks the operating system (the OS) to flush the system buffers for the open files. After that, the OS is responsible for ensuring that the data is actually flushed to disk.
Returns a non-negative value if successful; otherwise returns a negative value.