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[netCDF #NRE-269426]: ncdump -x with netCDF4 files

Hi Meg,

> I've installed netcdf-4.1.1 on an older virtual machine and have tested it 
> against various netcdf4 files.  In my testing, it does not give an explicit 
> error, but it does not generate any useful NcML.  In later versions, the 
> explicit error message was added.  It seems to me that you will not be able 
> to generate NcML with the C libraries/executable.

Ward is right that "ncdump -x" from version 4.1.1 doesn't work for any
netCDF-4 files that use features of the enhanced data model, such as
unsigned types, groups, strings, or user-defined types.  However, it
does provide what looks like useful NcML output for netCDF-4 classic
model files, which use the netCDF-4/HDF5 format but only features from
the classic netCDF-3 data model.  The netCDF-4.3.2 version of ncdump
likewise works to provide NcML output for netCDF-4 classic model files
when the "-x" option is used.  You can check whether a file is
netCDF-4 format or netCDF-4 classic model format using "ncdump -k" on
the file.

Ward is also right that netCDF-Java provides a Java ncdump that works
to provide NcML output even for netCDF-4 files that use the netCDF-4 
enhanced data model, which the C version of the utility can't yet handle.

--Russ

> I've done a bit of digging, and it appears that you might be able to use the 
> netcdf-java library to generate NcML for netcdf4 files, however.  Most of the 
> netcdf-java developers are out of the office for the upcoming Christmas 
> holiday, but I've done some testing by hand and it appears to work on my test 
> files.
> 
> After downloading the 'netcdfAll-4.5.jar' file from 
> http://www.unidata.ucar.edu/downloads/netcdf/index.jsp, I followed the 
> instructions found at 
> http://www.unidata.ucar.edu/software/thredds/current/netcdf-java/reference/manPages.html#ncdump,
>  e.g.
> 
> $ java -Xmx1g -classpath netcdfAll-4.5.jar ucar.nc2.NCdump 
> $HOME/Desktop/ncfiles/netcdf4_test.nc -ncml
> 
> Perhaps this solution would work for you? I wish I could say with more 
> confidence that netcdf4 support was implemented completely, but it should be 
> fairly easy to test.
> 
> I hope this helps,
> 
> -Ward
> 
> 
> > Hello,
> >
> > We've encountered a strange situation where someone with ncdump version
> > 4.1.1 is able to run ncdump with the -x flag on netCDF4s, whereas those of
> > us with later versions (4.3.2) cannot. My understanding was the NCML
> > extraction feature had never been implemented for netCDF4, but apparently
> > this is incorrect. Can you let me know what the status is? If possible,
> > we'd like to run ncdump -x on netCDF4s.
> >
> > Thanks,
> >
> > Meg Tilton
> >
> > --
> > Margaret Tilton
> > Cooperative Institute for Research in Environmental Sciences (CIRES) at
> > University of Colorado at Boulder and
> > NOAA National Geophysical Data Center, Solar and Terrestrial Physics
> > Division
> > 325 Broadway, E/GC2
> > Boulder, Colorado 80305
> > 303-497-6223
> >
> >

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



Ticket Details
===================
Ticket ID: NRE-269426
Department: Support netCDF
Priority: Normal
Status: Closed