The HDF_SD_FILEINFO procedure retrieves the number of datasets and global attributes in an HDF file.
            Examples
            
            SDinterface_id = HDF_SD_START('demo.hdf', /CREATE)
            
            HDF_SD_ATTRSET,SDinterface_id, 'TITLE', 'MYTITLE'
            
            HDF_SD_ATTRSET,SDinterface_id, 'TITLE2', 'MYTITLE2'
            
            SDdataset_id = HDF_SD_CREATE(SDinterface_id, 'var1', [10,3])
            
            HDF_SD_FILEINFO, SDinterface_id, datasets, attributes
            
            HELP, datasets, attributes
            
            HDF_SD_ENDACCESS, SDdataset_id
            
            HDF_SD_END, SDinterface_id
            IDL Output
            DATASETS LONG = 1
            ATTRIBUTES LONG = 2
            Syntax
            HDF_SD_FILEINFO, SDinterface_id, Datasets, Attributes
            Arguments
            SDinterface_id
            An SD interface ID as returned by HDF_SD_START.
            Datasets
            A named variable in which the total number of SD-type objects (i.e., the number of datasets + the number of dimensions) in the file is returned.
            Attributes
            A named variable in which the number of global attributes in the file is returned.
            Keywords
            None 
            Version History
            
            See Also
            HDF_SD_ATTRFIND, HDF_SD_ATTRINFO, HDF_SD_START