NetCDF-4 Filter QuickStart

Table of Contents

• NetCDF-4 Filter QuickStart
  • Building and Installing the Interface Libraries
  • Using the Interface Libraries at Run-time
  • Example Workflow (blosc)

NetCDF-4 Filter QuickStart

For full Filters documentation, see NetCDF-4 Filter Support.

The libnetcdf.so library cannot talk to plugin libraries directly. Instead, it requires an "interface" library, which acts as a go-between. The interface libraries are built by the netCDF libraries, when the underlying plugin libraries are detected during configure/build.

Building and Installing the Interface Libraries

When configuring netcdf via either the configure script or via cmake, you'll need to specify the location to install the interface libraries, as follows:

• configure: --with-plugin-dir=<absolutely directory>
• cmake: -DPLUGIN_INSTALL_DIR=<absolutely directory>

After compiling and installing libnetcdf, the interface libraries for those filters detected will be installed in the user-specified <absolute directory>.

Using the Interface Libraries at Run-time

For historical reasons, libnetcdf uses the environmental variable HDF5_PLUGIN_PATH to local the interface libraries at run-time.

Example Workflow (blosc)

From scratch, the steps to get this to work are as follows, and assumes libhdf5 was installed.

1. Install the filter library, and the associate development headers.
2. Configure netCDF with --enable-plugins and --with-plugin-dir=$HOME/netcdf-plugins
3. Ensure blosc is specified in the generated libnetcdf.settings file.
   
4. Run make, make install.

Once built and installed, set the environmental variable HDF5_PLUGIN_PATH=$HOME/netcdf-plugins.

The reason this works is because:

1. NetCDF builds the interface library.
2. ncdump knows where to find the interface library because HDF5_PLUGIN_PATH is set.