NCL: Write netCDF4 opaque data

Support for NetCDF-4 files is in beta-testing in V6.1.1.
We encourage people to test it out and give us feedback on our ncl-talk email list.

Below is a script which demonstrates how to read/write NetCDF4 opaque data.

Read NetCDF4 opaque data from a file generated from NetCDF opaque example code.

 fn = "$NCARGTEST/nclscripts/nc4_files/opaque.nc"

 fori = addfile(fn, "r")

;print(fori)
;printVarSummary(fori)

 ori_v = fori->var_defined_by_netcdf_user

 ori_nv = dimsizes(ori_v)
 
;print(ori_nv)
;print(ori_v)

 var_size = 1
 do n = 1, dimsizes(ori_nv) - 1
    var_size = ori_nv(n) * var_size
 end do

;print(var_size)

Create a file to write NetCDF4 string data.

;===================================================================
 setfileoption("nc", "Format",  "NetCDF4")

 fn = "ncl_wrt_opaque.nc"
 system("/bin/rm -f " + fn)
 fo = addfile(fn, "c")

Define some file attributes:

;===================================================================
 fAtt               = True            ; assign file attributes
 fAtt@title         = "NCL generated netCDF file with enum"
 fAtt@source_file   = fn
 fAtt@Conventions   = "None"
 fAtt@creation_date = systemfunc("date")

;print(fAtt)

 fileattdef(fo, fAtt)

Define dimensions:

;===================================================================
 nvals   = ori_nv(0)
 dimNames = (/"opaque_base_size"/)
 dimSizes = (/ nvals   /)
 dimUnlim = (/ False    /)
 filedimdef(fo, dimNames, dimSizes, dimUnlim)

Define the variable:

;===================================================================
 var_name = "opaque_variable"
 fileopaquedef(fo, "opaque_type", var_name, var_size, dimNames)

Write the compound data out, and close the file:

;===================================================================
 fo->$var_name$ = (/ori_v/)

 delete(fo)

This script produced (use "ncl_filedump ncl_wrt_opaque.nc"):

Variable: f
Type: file
filename:       ncl_wrt_opaque
path:   ncl_wrt_opaque.nc
User Defined Types:
    opaque_type
    {
    };

attributes:
    creation_date       :       Mon Jan 28 15:22:13 MST 2013
    Conventions :       None
    source_file :       ncl_wrt_opaque.nc
    title       :       NCL generated netCDF file with enum

dimensions:
    opaque_base_size    = 3

variables:
    opaque_variable:    [ 3  ]