0 for success and a non-zero flag for failure to open the dataset as a netCDF file, however if the file is not in the current working directory then the specification must include the path on the local file system.  (Ferret's "USE" command searches the directories that are included in the FER_DATA environment variable; the TEST_OPENDAP function does not.)  It does not operate on file types other than netCDF files.</p>
<pre>
yes? LIST test_opendap ("myfile.nc")
      VARIABLE : TEST_OPENDAP ("myfile.nc")
 