Install udunits with Homebrew, apk, apt, MacPorts, Nix, zypper, dnf

Project links

• Homepage
• Repository
• Upstream docs
• Package manager page

Commands and aliases

• udunits2

Project history

The current UDUNITS-2 line replaced the original UDUNITS-1 implementation while preserving broad compatibility. The official manual describes UDUNITS-2 as a C library, the `udunits2` unit-definition and conversion utility, and an extensive XML database of units.

UDUNITS-2 changed the older package in several concrete ways: non-ASCII unit strings, logarithmic units, persistent value converters, a revised API, and an XML unit database with import support. The manual also notes that a version 1 C API is included for backward compatibility, making it a transition package as well as a new implementation.

The changelog shows the project continuing through many 2.1 and 2.2 releases, with work on the command-line utility, Windows and CMake builds, unit database corrections, timestamp parsing, and portability fixes. Version 2.2.28 was published in December 2020 with documentation and release-engineering changes.

Adoption history

UDUNITS is part of the broader Unidata scientific software ecosystem, alongside tools such as netCDF. Its adoption pattern is typical of scientific infrastructure packages: it is rarely the end-user application, but it becomes a dependency below weather, climate, geoscience, and data-processing software that need consistent physical-unit parsing and conversion.

The package-manager metadata in this batch shows the same infrastructure role across Unix-like ecosystems: Homebrew ships `udunits`, Debian and Ubuntu expose `libudunits2-0`, Fedora uses `udunits2`, and MacPorts and Nix also package it. That spread reflects a library that downstream scientific stacks expect to find from the system package manager.

How it is used

Library users call UDUNITS to parse unit strings, obtain binary unit representations, manipulate units arithmetically, and build converters between compatible units. Command-line users use `udunits2` to inspect unit definitions and convert numeric values.

The XML unit database is a central usage point. The official documentation lists separate XML files for SI prefixes, SI base and derived units, SI-accepted units, and common non-SI units, and explains that the database is user-extensible.

Why package nerds care

UDUNITS is a classic scientific packaging dependency: small on the command line, important in ABI/API terms, and easy to overlook until a build of a larger scientific tool fails because unit parsing is missing. Its value to package nerds is that it externalizes a shared, curated unit database and conversion library instead of duplicating unit logic in every project.

The package is also interesting because it straddles eras. It keeps compatibility with older UDUNITS-1 users while presenting a UDUNITS-2 API and XML database, so distribution maintainers care about headers, shared-library paths, data-file locations, and versioned downstream expectations.

Timeline

• 2009: UDUNITS-2 2.1.0 added a UDUNITS-1 compatibility API inside the new library.
• 2011: The official GitHub repository was created.
• 2014: UDUNITS-2 2.2.x development focused on documentation, CMake, Windows support, and unit database fixes.
• 2020-12-28: UDUNITS 2.2.28 was published.

Related projects

• UDUNITS is published by NSF Unidata/UCAR and sits near other Unidata tools such as netCDF in scientific data workflows.
• The original UDUNITS-1 package is directly related: UDUNITS-2 documents both differences from UDUNITS-1 and a compatibility C API.

Sources

• The official CHANGE_LOG in the repository records 2.1.x, 2.2.x, and 2.2.28 release details.
• https://docs.unidata.ucar.edu/udunits/current/ describes UDUNITS-2, its components, differences from UDUNITS-1, XML database, installation, and support.
• https://github.com/Unidata/UDUNITS-2 is the official repository and describes the package as an API and utility for arithmetic manipulation of physical units.
• https://www.unidata.ucar.edu/software/udunits is the official product page for the package.
• source_facts.package-manager lists package names across Homebrew, Debian, Fedora, MacPorts, Nix, Ubuntu, and openSUSE.