cfchecker 2.0.6

Notes on CDMS install

The CDMS module is part of the CDAT distribution available from the PCMDI software portal (http://www2-pcmdi.llnl.gov/cdat/).

You can either install the entire CDAT distribution or alternatively use the CDAT-lite package.

Notes on UDUNITS-2 install

The UDUNITS-2 package can be obtained from the unidata website (http://www.unidata.ucar.edu/software/udunits)

To run the CF checker

Once you have both UDUNITS-2 and CDMS installed you need to complete the following steps in order to run the CF Checker.

1. Make sure that the location of the cdms library is in your PYTHONPATH

   E.g. export PYTHONPATH=/home/rsh/software/CDAT-5.2-cdms/lib/python2.5/site-packages

2. Make sure that the path to the udunits libraries are in the system library path or alternatively set the environment variable LD_LIBRARY_PATH

   E.g. export LD_LIBRARY_PATH=$PREFIX/lib

   where $PREFIX is the –prefix option you passed to the configure script when installing udunits.

3. Depending on the platform you are installing on, you may need to edit the name of the udunits2 library in the cfchecks.py script. If the name of the library is anything other than libudunits2.so then you will need to modify, as appropriate, the line

   udunits=CDLL(“libudunits2.so”)

4. You may also need to modify the path to the python interpreter at the top of the cfchecks.py script.

5. Run the checker by typing:

   cfchecks.py <netCDF_file.nc>

Environment Variables

The following parameters can be set on the command-line or through environment variables:

1. UDUNITS : The path to udunits2.xml. Usually $UDUNITS_HOME/share/udunits/udunits2.xml

2. CF_STANDARD_NAMES : The path or URL to the CF standard names table

3. CF_AREA_TYPES : The path or URL to the CF area types tables

If you have any problems or comments please contact Rosalyn Hatcher (r.s.hatcher@reading.ac.uk)

Wrapper script

A wrapper to cfchecks, called “cf-checker”, is provided in the src/ directory, which will maintain local copies of the standard names table and the area types table, and will refresh these local copies only if the age of the file (based on its modification time) is more than a specified maximum, defaulting to 1 day. This allows for running the checker repeatedly without refetching the tables on each invocation, while still keeping them reasonably up to date.

For a usage message, type “cf-checker -h”

Note that the wrapper defaults to storing the downloaded files in /var/spool/cf-checker, so if the script is used unmodified then this directory should be created or else an alternative value should be passed as a command line option (“-d”). Ensure either that all users have write permission to the directory used, or else that a user that does have write permission runs a cron job to refresh the tables. For the latter purpose, it is permissible to run the wrapper without specifying any data files to check, in which it will do no more than update the tables; this is still conditional on age, so for this purpose it is recommended to run the wrapper with a maximum age of zero (“-t 0”), and to run the cron job at intervals not exceeding the default maximum age.

The wrapper is maintained by CEDA and not by NCAS CMS.