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Re: 20030304:Question about get_var

>To: address@hidden
>From: Janet Anstett <address@hidden>
>Subject: Question about get_var
>Organization: UCAR/Unidata
>Keywords: 200303032232.h23MWC314778

Hi Janet,

> I am using the C++ interface to netcdf version 3.5.0.  I am using
> get_var to get the variable ids from an existing netcdf file.
> Sometimes the variable that I am looking for does not exist in a
> particular file.  I am trying to figure out a way to check the return
> value to see if I did get a variable id or it didn't work.  I have
> checked the documentation and could not tell whether there is a way to
> do this.  I checked the web lists and couldn't find anything
> relevant.  Basically when I use get_var on a variable that doesn't
> exist in the file, I get the following error message:
> ncvarid: ncid 3: Variable not found
> I would like to be able to check whether the variable exists in the
> file without the program erroring out.  Is there a way to do this?

Yes, you need to change the default NcError::Behavior from
verbose_fatal to something more appropriate, such as silent_nonfatal
or verbose_nonfatal.  That way, you can check the value of the get_var
method and the library won't just exit.  For documentation of the
NcError class, see

   http://www.unidata.ucar.edu/packages/netcdf/cxxdoc.html#SEC18

As an example, just declaring:

    NcError* xerror = new NcError(NcError::silent_nonfatal);

will change the error handling behavior until the xerror object is
destroyed, either explicitly or just by going out of scope.

--Russ