NetCDF Attribute Inquiry

[Alex Schuster <alex(at)pet.mpin-koeln.mpg.de>]

Hi!

I am reading NetCDF files. I do not know for sure which of the
attributes are really stored in the file, so I use NCDF_ATTINQ() to
check before.

With missing attributes, there are two problems:

1) I always get a message like that:
% NCDF_ATTINQ: Attribute inquiry failed, name "somthing" already in use.
This doesn't look good, but I can live with that. No idea why it it
tells me that the name is already being used, because it is not.

2) This one is worse: sometimes the result structure of NCDF_ATTINQ()
does not have a datatype of 'UNKNOWN', but of 'BYTE'. With a random
length. Another NCDF_ATTINQ() gives a different result. Any idea what's
happening here? 

My workaround so far is the usage of this function:

function attribute_there, id, varid, name
 result = ncdf_attinq( id, varid, name )
  if ( result.datatype ne 'UNKNOWN'  $
		and  result.length gt 0  $
		and  result.length lt 1000 ) then begin
    result = ncdf_attinq( id, varid, name )
    if ( result.datatype ne 'UNKNOWN'  $
		and  result.length gt 0  $
		and  result.length lt 1000 ) then begin
      return, 1
    endif
  endif
return, 0
end

I check two times, and I also check for not-too-crazy length fields. I
guess this will work most of the time, but it's not perfect and will
fail some time.

        Alex
-- 
  Alex Schuster     Wonko@weird.cologne.de          PGP Key available
                    alex@pet.mpin-koeln.mpg.de