pro show_sds,filename,tags=tags
;   show variables from HDF files
;   usage: idl> read_sds_one,'filename',tags=tags
;   return the tags with the names of the variables  
;                 chuntao liu
;                           6/28/05

m=0
tags=filename
sdsfileid = hdf_sd_start(filename,/read)
hdf_sd_fileinfo,sdsfileid,numsds,ngatt
for i = 0, numsds - 1 do begin
   sds_id = hdf_sd_select(sdsfileid, i )
   hdf_sd_getinfo, sds_id, name = na, ndim = nd,type= typ, label=label
   if keyword_set(tag_label) and strlen(label) gt 0 then na=label
   tics=strsplit(na,' ',/extract)
   if(n_elements(tics) gt 1) then na=tics[0]+'_'+stringit(long(tics[1]))
   iftags=where(strupcase(na) eq tags)
   if(iftags[0] ge 0) then na=na+'_'+stringit(i)
   print,na,typ,nd,format='(a30,a10,i3)'
   tags=[tags,na]
   hdf_sd_endaccess,sds_id
endfor
hdf_sd_end,sdsfileid
end