Reading NetCDF in C Software Documentation

Usage

 cdf2c [-v] [-o outputFile] inputFilePath

This procedure creates a c routine to read in the data from a NetCDF file. The default mode, non-verbose output, outputs only the varaible data to the c routine.

The variables and global attributes have identical names to the variable and global attribute names in the NetCDF file. The attributes associated with a given variable have names preceded by the associated variable name.

[-v]

If this flag is set then the cdf2c program creates verbose output. All variable and global attributes in the netCDF file will be included in the resultant c routine.

[-o outputFile]

This flag allows you to enter an optional output filename for the routine produced by the program. The default is for the output to be written to stdout.

inputFilePath

The full path to the netCDF file for which you wish to create a c routine to read the data.

Prerequisites

This program CANNOT be compiled without the netCDF library. The source code for the netCDF library can be obtained via anonymous ftp to ftp.unidata.ucar.edu. The necessary files are located in the /pub/netcdf directory.

Additionally, the Makefile provided uses the gcc compiler to compile the program. You may substitute for your local compiler, but if you do, you will need to modify the Makefile to use the flags appropriate to your particular compiler. You may also obtain the gcc compiler, if you do not have it, via anonymous ftp to prep.ai.mit.edu. The gcc compiler is located in the /pub/gnu directory along with a suite of other free goodies.

Please read the Readme included with this release to ensure that the code compiles properly.

Example

Assuming you have met all of the prerequisites, and that you have followed
the instructions in the Readme file.


your_machine 1 > make  
your_machine 2 > cdf2c -v -o netCDF_reader.c /path_to_data_file/data_file.cdf

The resulting c routine will be placed in the file netCDF_reader.c

netCDF_reader.c

//-------------------------------------------------------------------------
//
//  This code was generated by cdf2c to read the netCDF data from the 
//  file.cdf file into memory.
//
//  NOTE:  The code creates global variables, but you may move the variable
//         definitions inside the read_netCDF_file procedure if you wish.
//         The code REQUIRES the netCDF C libraries to run, and assumes that
//         netcdf.h is in the common include path.  DON'T FORGET to link with
//         -lnetcdf -lsun when you compile the code.
//
//  This file contains the following routines:
//
//     read_netCDF_file - reads the data from the given netCDF file into memory
//
//  History:
//  Date       long_name          Action
//  ---------  ------------  -----------------------------------------------
//  ?? ??? ??  CIDS          Work in Progress.
//
//-------------------------------------------------------------------------

#include 

// Variable definitions.  The comments contain the dimension names.
double llt_lon[20];                         // numofsamples
char   llt_lon_long_name[10];
char   llt_lon_units[8];
double llt_lat[20];                         // numofsamples
char   llt_lat_long_name[9];
char   llt_lat_units[8];
double llt_time[20];                        // numofsamples
char   llt_time_long_name[5];
char   llt_time_units[8];
double variable1[20];                       // numofsamples
char   variable1_long_name[19];
char   variable1_units[27];
long   i_iets[5][2];                        // nof, two
char   i_iets_long_name[27];
char   i_iets_units[8];
char   srcflnms[5][300];                    // nof, noc
char   srcflnms_long_name[18];
char   srcflnms_units[5];
char   platform[11];
char   instrument[13];
char   original_data_source[39];
char   original_data_date[24];
char   original_data_file[60];
char   conversion_software[43];
char   conversion_technician[39];
char   conversion_date[24];
char   source_file[61];


void 
read_netCDF_file ()
{
   //# func_description
   //  This routine reads the data from file.cdf into memory.

   int   fd;
   long  start[MAX_NC_VARS];
   long  end[MAX_NC_VARS];

   // Open the netCDF file.
   fd = ncopen("file.cdf", NC_NOWRITE);

   // Initialize start so all elements are zero.
   bzero(start, MAX_NC_VARS * sizeof(long));

   // Read in the variables and their attributes.
   // Read: llt_lon.
   end[0] = 20;
   ncvarget(fd, 0, start, end, llt_lon);
   // Read: llt_lon_long_name.
   ncattget(fd, 0, "long_name", llt_lon_long_name);
   // Read: llt_lon_units.
   ncattget(fd, 0, "units", llt_lon_units);

   // Read: llt_lat.
   end[0] = 20;
   ncvarget(fd, 1, start, end, llt_lat);
   // Read: llt_lat_long_name.
   ncattget(fd, 1, "long_name", llt_lat_long_name);
   // Read: llt_lat_units.
   ncattget(fd, 1, "units", llt_lat_units);

   // Read: llt_time.
   end[0] = 20;
   ncvarget(fd, 2, start, end, llt_time);
   // Read: llt_time_long_name.
   ncattget(fd, 2, "long_name", llt_time_long_name);
   // Read: llt_time_units.
   ncattget(fd, 2, "units", llt_time_units);

   // Read: variable1.
   end[0] = 20;
   ncvarget(fd, 3, start, end, variable1);
   // Read: variable1_long_name.
   ncattget(fd, 3, "long_name", variable1_long_name);
   // Read: variable1_units.
   ncattget(fd, 3, "units", variable1_units);

   // Read: i_iets.
   end[0] = 5;   end[1] = 2;
   ncvarget(fd, 6, start, end, i_iets);
   // Read: i_iets_long_name.
   ncattget(fd, 6, "long_name", i_iets_long_name);
   // Read: i_iets_units.
   ncattget(fd, 6, "units", i_iets_units);

   // Read: srcflnms.
   end[0] = 5;   end[1] = 300;
   ncvarget(fd, 7, start, end, srcflnms);
   // Read: srcflnms_long_name.
   ncattget(fd, 7, "long_name", srcflnms_long_name);
   // Read: srcflnms_units.
   ncattget(fd, 7, "units", srcflnms_units);

   // Read in the Global Attributes.
   // Read: platform.
   ncattget(fd, 0, "platform", platform);

   // Read: instrument.
   ncattget(fd, 1, "instrument", instrument);

   // Read: original_data_source.
   ncattget(fd, 2, "original_data_source", original_data_source);

   // Read: original_data_date.
   ncattget(fd, 3, "original_data_date", original_data_date);

   // Read: original_data_file.
   ncattget(fd, 4, "original_data_file", original_data_file);

   // Read: conversion_software.
   ncattget(fd, 5, "conversion_software", conversion_software);

   // Read: conversion_technician.
   ncattget(fd, 6, "conversion_technician", conversion_technician);

   // Read: conversion_date.
   ncattget(fd, 7, "conversion_date", conversion_date);

   // Read: source-file.
   ncattget(fd, 8, "source-file", source_file);

   // Close the netCDF file.
   ncclose(fd);
}

You may now add a main and any other functions you wish to manipulate the 
data to the routine in netCDF_reader.c.

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