[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[netCDF #GCF-527136]: netCDF General - ncdump dumps exactly what?

Hi George,

No, ncdump dumps the whole file, unless you explicitly select a subset of 
variables to dump with the "-v varlist" option, or explicitly dump only the the 
header metadata with the "-h" or "-c" option.

However, if you have a lot of values in the file that are "fill values", either 
because they were never explicitly written or because they were written as fill 
values (which can be specified using the "_FillValue" attribute or using a 
default fill value for each type), then ncdump displays such values using the 
underscore character, for example

  data:
    var1 = _, _, _, _, ... ;

If the original file had lots of doubles (8 bytes each) that were displayed in 
the ncdump output as fill values (3 bytes each), the output could approach 
being only 37.5% as large as the original file, but it would not be possible 
for a 111 MB file to have an ncdump output of only 550K.  So I agree, something 
is wrong.  You should be able to compute the size of the netCDF file from just 
the information in the header.  It's possible that lots of bytes have been 
concatenated onto the end of the file and there would be no way to know that 
through just the netCDF interface.  If you're still puzzled, compare the output 
of "ncdump -c" of the original file with the output of "ncdump -c" of the 
ncgened file and see what the difference is.

--Russ


Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: GCF-527136
Department: Support netCDF
Priority: Normal
Status: Closed