Re: [netcdfgroup] Using file:// protocol to retrieve opendap data...

  • To: Dennis Heimbigner <dmh@xxxxxxxxxxxxxxxx>
  • Subject: Re: [netcdfgroup] Using file:// protocol to retrieve opendap data...
  • From: ed zaron <zaron@xxxxxxxxxxxx>
  • Date: Tue, 11 Jan 2011 09:27:10 -0800
Hi Dennis,

Thanks a lot for posting the revised source. The new client works on the DODS 
files.

I downloaded a test file from the OpenDAP test site:
http://test.opendap.org/dap/netcdf/examples/ECMWF_ERA-40_subset.nc.html

This returned a file with .nc.dods extension:
ECMWF_ERA-40_subset.nc.dods

It took a few tries to figure out the filename syntax, though, as recorded 
below.

The following commands ~do not~ open the file:

nigiri:Downloads ezaron$ ncdump -h ./ECMWF_ERA-40_subset.nc
ncdump: ./ECMWF_ERA-40_subset.nc: No such file or directory

nigiri:Downloads ezaron$ ncdump -h ./ECMWF_ERA-40_subset.nc.dods
ncdump: ./ECMWF_ERA-40_subset.nc.dods: NetCDF: Unknown file format

nigiri:Downloads ezaron$ ncdump -h file://./ECMWF_ERA-40_subset.nc
ncdump: file://./ECMWF_ERA-40_subset.nc: NetCDF: I/O failure

The following commands ~do~ work:
ncdump -h file://ECMWF_ERA-40_subset.nc
ncdump -h file:///Users/ezaron/Downloads/ECMWF_ERA-40_subset.nc

Thanks again!

-Ed


On Jan 10, 2011, at 4:21 PM, Dennis Heimbigner wrote:

> The netcdf snapshot
> (ftp://ftp.unidata.ucar.edu/pub/netcdf/snapshot/netcdf-4-daily.tar.gz)
> available TOMORROW (Tuesday)
> now supports the ability to access opendap data stored in files.
> 
> If you have a file called, say, dataset.dods, it is expected that
> it contains the on-the-wire data for a request to an opendap server.
> Such a file can be created using, for example, wget or a web browser.
> Similarly, one can save .das and .dds data in files.
> 
> Suppose you have such a file at absolute path /home/abc/dapdata.dods.
> You should now be able to access it using, for example the command:
>    ncdump file:///home/abs/dapdata
> You could also use nccopy instead of ncdump.
> NOTE: the final .dods is left off.
> 
> There are some things to note:
> 1. You must have at least a .dods file (e.g. dataset.dods).
> 
> 2. If there is also a /home/abs/dapdata.das,
>   it will be used to obtain attributes.
> 
> 3. If there is a /home/abs/dapdata.dds
>   it will be used.  If this does not exist,
>   then the dds part of the .dods file will be used.
> 
> If you are in a position to try this out, please do so
> and let me know if there are any problems.
> 
> =Dennis Heimbigner (dmh@xxxxxxxx)
> Unidata

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