NC4F

NC4F is a modern Fortran interface to the NetCDF C library. It provides a small in-memory model for NetCDF dimensions, attributes, variables, and groups. The library calls the NetCDF C API directly, thus the NetCDF Fortran library is not required.

What NC4F Can Do

The main purpose of this library is to experiment the feasibility of an xarray-like programming style in modern Fortran that write and read through some unified routines. For example:

• Build a NetCDF data model with DATARRAY and DATASET;
• Write a data model to a NetCDF file with TO_NETCDF;
• Open a NetCDF file and retrieve variables with OPEN_NETCDF and GET_VARIABLE;
• Extract intrinsic Fortran data from an attribute or variable with EXTRACT;

A First Program

Here is a taste of how you can use this library:

program main

  use :: nc4f
  implicit none
  
  real, parameter :: temperature(3) = [289.4, 290.1, 288.7]
  real, pointer :: temperature_vals(:)
  type(netcdf_type) :: nc
  type(variable_type) :: temperature_write, temperature_read
  
  temperature_write = datarray( &
    & "temperature", temperature, dims=["station".dim.3], &
    & atts=["units".att."K", "long_name".att."Near-surface air temperature"])
  call to_netcdf("temperature.nc", temperature_write)
  
  nc = open_netcdf("temperature.nc", "r")
  temperature_read = get_variable(nc, "temperature")
  call close_netcdf(nc)
  call extract(temperature_read, temperature_vals)
  
  print *, temperature_read
  print *, temperature_vals

end program main

What NC4F Cannot Do

NC4F is not intended to replace the well-established NetCDF Fortran library or wrappers such as nc4fortran and neasy-f. NC4F is intentionally designed to focus on a small subset of the NetCDF data model. It does NOT currently support:

• classic NetCDF format;
• user-defined types, the NetCDF STRING type and unsigned primitive types;
• NetCDF-4 storage controls, such as chunking, compression, shuffle/checksum filters, endianness, and custom fill values;
• parallel, in-memory, or diskless I/O;
• advanced variable access, such as mapped or multi-slab I/O and strided writes; or metadata mutation operations, such as renaming or deleting dimensions, variables, groups, and attributes.

Build and Installation

NC4F requires a modern Fortran compiler, the NetCDF C library, and pkg-config.

Build and test with fpm

From a checkout of this repository, build and run the test suite with:

fpm test --profile debug --flag "$(pkg-config --cflags --libs netcdf)"

Generated NetCDF test artifacts are written to build/test-results/.

Use NC4F as an fpm dependency

Add nc4f to the consuming package's fpm.toml, then link the NetCDF C library in that package:

[dependencies]
nc4f = { git = "https://github.com/han190/nc4f.pack.git" }

[build]
link = ["netcdf"]