[netCDF #AOB-147341]: Sample C++ program to write variables in to an existing (empty) NetCDF file

 Hi Lyon,

> I have looked at your sample programs C++ at :
> http://www.unidata.ucar.edu/software/netcdf/examples/programs/
> and have found them to be quite useful.  However, I found that in all
> the examples associated with writing variables
> in to a NetCDF file, the program always creates a new NetCDF file first
> and then writes the variables in to it.
> 
> Could you please send me a sample C++ program which writes variables
> (their values) in to a currently existing NetCDF
> file? - e.g. create a dummy NetCDF file and then close it.  Thereafter,
> re-open it and then write some variables in
> to it.  To be more specific, I am looking for a routine to write a time
> value and vector values for x, y, z as my
> code runs i.e. where the time dimension will be unlimited and I will be
> writing one time record of info at a time.

You can close an existing file with the close() method, as in 

   // First create a file with no data. 
   NcFile file0("simple.nc", NcFile::Replace);   
   // Check to see if the file was created.
   if(!file0.is_valid())
      return NC_ERR;
   // close the empty file
   file0.close();

and then reopen it for writing using the same or a different variable, as in

   NcFile file1("simple.nc", FileMode=NcFile::Write);
   if(!file1.is_valid())
      return NC_ERR;

Now you can define dimensions, variables, and atributes and add data to file1
using the C++ methods as in the examples.

If you want to append data to an existing file that already has N records of
a four-dimensional variable dimensioned with (time, x, y, z), where time is 
the unlimited dimension, just call setcur with

  if(!file1.setcur(N, 0, 0, 0))
      return NC_ERR;

then call put with the data for record N+1, as in

  NcVar var = file1.get_var("varname");
  if(!var)
     return NC_ERR;

  if(!var.put(values, 1, NX, NY, NZ))
     return NC_ERR;

where "values" is a block of data values for one record.

--Russ

Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: AOB-147341
Department: Support netCDF
Priority: Normal
Status: Closed