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[netCDF #ZDR-128646]: Ncfile for cpp

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  • Subject: [netCDF #ZDR-128646]: Ncfile for cpp
  • Date: Tue, 31 Aug 2010 16:18:05 -0600
Hi Camilla,

> I am writing a C++ program to read the data in a netcdf file. In the
> script, I use 'Ncfile' to read the .nc file. However, the compiler said
> that the function 'Ncfile' was not found. Would you please give me some
> advice?
> 
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> 
> using namespace std;
> #include <iostream>        // This is a key C++ library
> #include "netcdfcpp.h"
> 
> string dir ("G:/result/");
> string code ("us0000");
> const string path = dir + code;
> const string fil = path + "/" + "wrfout_" + code + ".nc";
> 
> int main ()
> {
> NcFile file(fil, NcFile::ReadOnly);
> if ( !file->is_valid() ) {
> delete fil;
> exit(1);
> }
> NcVar* var = fil->get_var("P");
> if(var)
> printf("variable's name is %s/n", var->name());
> system("pause");
> return 0;
> }

Yes, the netCDF C++ library was developed in the mid-1990's and is
showing its age (no use of Exceptions, Templates, or namespaces, for
example).  The netCDF Java API is much more up-to-date.  An experimental
new C++ API for netCDF-4, contributed by Lynton Appel, is available in
the 4.1.1 release and is built if you configure with --enable-cxx4, but
it still needs a little more work to support netCDF classic files.

The current C++ API is just a thin wrapper layer on top of the C 
library, so in particular, it takes C char* arguments instead of C++ 
string arguments where character strings are required.  So if you change
all the string declarations to the corresponding char* or char[]
declarations, things should work:

using namespace std;
#include <iostream>        // This is a key C++ library
#include "netcdfcpp.h"
#include <strings.h>

char dir[] = "G:/result/";
char code[] = "us0000";
const char *path = strcat(dir, code);
char fil[NC_MAX_NAME];
 
int main ()
{
   sprintf(fil, "%s/wrfout_%s.nc", path, code);
   NcFile file(fil, NcFile::ReadOnly);
   if ( !file.is_valid() ) {
        delete fil;
        exit(1);
        }
        NcVar* var = file.get_var("P");
        if(var)
        printf("variable's name is %s/n", var->name());
   system("pause");
   return 0;
}

--Russ


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



Ticket Details
===================
Ticket ID: ZDR-128646
Department: Support netCDF
Priority: Normal
Status: Closed