simple_nc4.c File Reference

Basic NetCDF-4/HDF5 format file creation and format detection. More...

#include <stdio.h>
#include <stdlib.h>
#include <netcdf.h>

Macros
#define	FILE_NAME   "simple_nc4.nc"
#define	NDIMS   2
#define	NX   6
#define	NY   12
#define	ERRCODE   2
#define	ERR(e)   {printf("Error: %s\n", nc_strerror(e)); exit(ERRCODE);}

Functions
int	main ()

Detailed Description

Basic NetCDF-4/HDF5 format file creation and format detection.

This example introduces the NetCDF-4 format, which uses HDF5 as the underlying storage layer. NetCDF-4 provides enhanced features including compression, chunking, multiple unlimited dimensions, and user-defined types while maintaining backward compatibility with the NetCDF API.

The program creates a simple 2D array using the NC_NETCDF4 flag and demonstrates format detection to verify the file was created in NetCDF-4/HDF5 format rather than classic NetCDF format.

Learning Objectives:

• Understand NetCDF-4 format and its HDF5 foundation
• Learn to create NetCDF-4 files with NC_NETCDF4 flag
• Master format detection using nc_inq_format() and nc_inq_format_extended()
• Recognize differences between classic and NetCDF-4 formats
• Prepare for advanced NetCDF-4 features (compression, chunking, groups)

Key Concepts:

• NetCDF-4 Format: HDF5-based format with enhanced features
• NC_NETCDF4 Flag: Creation flag to specify NetCDF-4 format
• Format Detection: Runtime identification of file format type
• HDF5 Backend: Underlying storage technology for NetCDF-4
• Backward Compatibility: NetCDF-4 files readable with NetCDF-4 library

NetCDF-4 vs Classic Comparison:

• Classic: Simple format, 2GB limits (CDF-1) or 4GB variable limits (CDF-2/5)
• NetCDF-4: HDF5-based, compression, chunking, unlimited file/variable sizes
• Classic: One unlimited dimension maximum
• NetCDF-4: Multiple unlimited dimensions supported
• Classic: No compression or chunking
• NetCDF-4: Built-in compression filters and flexible chunking

Prerequisites:

• simple_2D.c - Basic NetCDF file operations
• format_variants.c - Understanding classic format types

Related Examples:

• f_simple_nc4.f90 - Fortran equivalent
• compression.c - NetCDF-4 compression features
• chunking_performance.c - NetCDF-4 chunking strategies
• multi_unlimited.c - Multiple unlimited dimensions
• user_types.c - User-defined compound types

Compilation:

gcc -o simple_nc4 simple_nc4.c -lnetcdf

Usage:

./simple_nc4
ncdump simple_nc4.nc
h5dump simple_nc4.nc  # View as HDF5 file

Expected Output: Creates simple_nc4.nc in NetCDF-4/HDF5 format containing:

• 2 dimensions: x(6), y(12)
• 1 variable: data(y, x) of type int
• Format: NC_FORMAT_NETCDF4 (HDF5-based)
• File is readable by both NetCDF-4 and HDF5 tools

Author

Edward Hartnett, Intelligent Data Design, Inc.

Date

2026

Macro Definition Documentation

ERR

#define ERR

(

e

)

{printf("Error: %s\n", nc_strerror(e)); exit(ERRCODE);}

ERRCODE

#define ERRCODE   2

FILE_NAME

#define FILE_NAME   "simple_nc4.nc"

NDIMS

#define NDIMS   2

NX

#define NX   6

NY

#define NY   12

Function Documentation

main()

int main

(

)