[gdal-dev] /vsicurl/ and gz files

[Kyle Shannon]

On Fri, Oct 11, 2013 at 7:13 AM, Jose Gomez-Dans <jgomezdans at gmail.com> wrote:
> Hello everyone,
>
> On 10 October 2013 19:58, Even Rouault <even.rouault at mines-paris.org> wrote:
>
>> Le jeudi 10 octobre 2013 20:33:49, Jose Gomez-Dans a écrit :
>> > Hi,
>> >
>> > I was wondering if it's possible to use /vsitar/ to have a peek in .gz
>> > files, such as this one:
>> >
>> > http://www.globalbedo.org/GlobAlbedo29/tiles/2004/h17v04/GlobAlbedo.2004001
>> > .h17v04.nc.gz
>>
>> This is a gzip file, not a .tar.gz file, so you would have to use /vsigzip
>> , and
>> as it is a gzip file over http, you have to combine it with /vsicurl
>
>
> I hadn't seen the /vsigzip/ option, but it's quite obvious! The /vsicurl/
> limitation isn't important, I just thought it'd be a nice way to brag about
> GDAL ;-) However, one problem still persists. While I can prod into the
> decompressed file (e.g. after I have gunzipped it), the following command
> still reports a problem, e.g:
>
> $ gdalinfo /vsigzip/GlobAlbedo.2004001.h17v04.nc.gz
> ERROR 1: netcdf error #-33 : NetCDF: Not a valid ID .
> at (netcdfdataset.cpp,~netCDFDataset,1446)
>
> gdalinfo failed - unable to open '/vsigzip/GlobAlbedo.2004001.h17v04.nc.gz'.
>
> gdalinfo --version
> GDAL 1.10.0, released 2013/04/24
>
> $ gunzip GlobAlbedo.2004001.h17v04.nc.gz
>
> $ gdalinfo GlobAlbedo.2004001.h17v04.nc.gz
> ERROR 4: `GlobAlbedo.2004001.h17v04.nc.gz' does not exist in the file
> system,
> and is not recognised as a supported dataset name.
>
> gdalinfo failed - unable to open 'GlobAlbedo.2004001.h17v04.nc.gz'.
>
> $ gdalinfo GlobAlbedo.2004001.h17v04.nc
> Driver: netCDF/Network Common Data Format
> Files: GlobAlbedo.2004001.h17v04.nc
> Size is 512, 512
> Coordinate System is `'
> Metadata:
>   NC_GLOBAL#Conventions=CF-1.4
> Subdatasets:
>   SUBDATASET_1_NAME=NETCDF:"GlobAlbedo.2004001.h17v04.nc":DHR_VIS
>   SUBDATASET_1_DESC=[1200x1200] DHR_VIS (32-bit floating-point)
> [....]
>
> Thanks!
> Jose
>
>
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As Even mentioned, the NetCDF driver doesn't use the VSI*L mechanism,
so you can't use /vsi*/ stuff with it unless you use
LD_PRELOAD=vsipreload.so, see above.

kss

-- 
Kyle