sd_id	IN:	SD interface identifier returned by SDstart
	num_datasets	OUT:	Number of data sets in the file
	num_global_attrs	OUT:	Number of global attributes in the file

	Purpose	Retrieves the number of data sets and the number of global attributes in a file.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) otherwise.
	Description	SDfileinfo returns the number of data sets in the parameter num_datasets and the number of global attributes in the parameter num_global_attrs. The term "global attributes" refers to attributes that are assigned to the file. The global attributes are created by SDsetattr using an SD interface identifier (sd_id) rather than a data set identifier (sds_id).
		The value returned by the parameter num_datasets includes the number of coordinate variable data sets. To determine if the data set is a coordinate variable, use SDiscoordvar.

	FORTRAN	integer function sffinfo(sd_id, num_datasets, num_global_attrs)
		integer sd_id, num_datasets, num_global_attrs