ruby-hdf5

Ruby bindings for the HDF5 library.

Scope

This gem currently provides practical high-level wrappers for:

• opening and creating files
• creating groups
• creating, writing, and reading one-dimensional numeric datasets
• reading and writing numeric attributes

Unsupported at this stage:

• string dataset read/write
• multidimensional array write

Integer datasets and integer attributes currently use native C int under the hood. Values outside that range are rejected with HDF5::Error to avoid silent overflow.

Group#list_datasets filters datasets from group entries by checking object type per entry. For very large groups, this may be slower than Group#list_entries.

Supported HDF5 Versions

• HDF5 1.10
• HDF5 1.14
• HDF5 2.x

HDF5 versions older than 1.10 are not supported.

Install

Add to your Gemfile:

gem 'ruby-hdf5'

Install:

bundle install

System library (libhdf5) is required.

Runtime Notes

• The gem loads libhdf5 through FFI.
• If the shared library cannot be found automatically, set HDF5_LIB_PATH.

Examples:

# Point to a directory containing libhdf5.so
export HDF5_LIB_PATH=/usr/lib

# Or point directly to the shared object
export HDF5_LIB_PATH=/usr/lib/libhdf5.so

Quick Start

Read an existing file

require 'hdf5'

HDF5::File.open('example.h5') do |file|
	group = file['foo']
	dataset = group['bar_int']
	p dataset.shape
	p dataset.dtype
	p dataset.read
end

Create and write a file

require 'hdf5'

HDF5::File.create('numbers.h5') do |file|
	file.create_group('values') do |group|
		group.create_dataset('ints', [1, 2, 3, 4])
	end
end

reopened = HDF5::File.open('numbers.h5')
p reopened['values']['ints'].read
reopened.close

Error Handling

High-level API failures raise HDF5::Error.

begin
	HDF5::File.open('missing.h5')
rescue HDF5::Error => e
	warn e.message
end

Development

After more than a decade, it is clear that the Ruby community does not have enough resources to sustainably maintain an HDF5 library. For that reason, development of this library is intentionally AI-assisted. Something is better than nothing.

Acknowledgement

https://github.com/edmundhighcock/hdf5

License

The gem is available as open source under the terms of the MIT License.