Can not nccopy a file with a _Netcdf4Dimid attribute

[kwilcox]

Environment Information

netCDF library version 4.4.1.1 of Dec 25 2016 19:06:13

• What platform are you using? (please provide specific distribution/version in summary)
  • Linux
• 32 and/or 64 bit?
  • 64-bit
• What build system are you using?
  • cmake
• Can you provide a sample netCDF file or C code to recreate the issue?
  • Yes (please attach to this issue, thank you!)

Summary of Issue

A file or DAP endpoint with a variable attribute of _Netcdf4Dimid will fail to download/convert to netCDF4. Originally discovered/reported here nco/nco#57.

Steps to reproduce the behavior

$ nccopy -7 -v z http://oceanmodeling.pmc.ucsc.edu:8080/thredds/dodsC/ccsra_2016a_phys_agg_zlevs/fmrc/CCSRA_2016a_Phys_ROMS_z-level_\(depth\)_Aggregation_best.ncd out.nc
NetCDF: String match to name in use
Location: file /feedstock_root/build_artefacts/recipe_root_1482692731718/work/netcdf-c-4.4.1.1/ncdump/nccopy.c; line 788

[DennisHeimbigner]

The Thredds server you are accessing is very old: 4.2.9.
The current is 4.6.10.

Since _Netcdf4Dimid is a reserved netcdf name, it should not be
possible to access it thru the netcdf API. But the Thredds
server by default uses the HDF5 Iosp to read the netcdf-4 file
and it is probable that the version of the Iosp the server is
using is not suppressing reserved attributes. I did a quick
check, and the latest thredds 4.6 server does properly suppress
_Netcdf4Dimid.

The only solutions I can think of are:

1. Get the server upgraded.
2. hack the netcdf-c library to do the suppression
3. hack nco to do the suppression.

I am not happy with #2 and I am sure Charlie would not be happy with #3.
Is a server upgrade at all feasible?

=Dennis Heimbigner
Unidata

[kwilcox]

I'm also against fixing this in netcdf-c or nco. I don't control the THREDDS server but I can reach out and see if they are willing to upgrade. I have a work-around in place to remove the attribute so it plays nicely with the rest of the workflow. Feel free to close!