dune

composable build system for OCaml projects

TLDR

Build the project

$ dune build

Run tests

$ dune test

Run an executable

$ dune exec [program]

Clean build artifacts

$ dune clean

Build and watch for changes

$ dune build --watch

Format code

$ dune fmt

Create new project

$ dune init project [name]

Dune is the standard build system for OCaml and Reason projects. It automatically discovers project structure, handles dependencies, and provides fast incremental builds with caching.Projects are configured with dune files using an S-expression syntax. Dune integrates with opam for package management and supports cross-compilation, multiple build contexts, and IDE integration.

PARAMETERS

build [targets]

Build specified targets or all.

test

Run tests.

exec program

Build and execute program.

clean

Remove build artifacts.

init component name

Initialize new component (project, library, executable, test).

fmt

Format source code using ocamlformat.

promote

Promote expected test outputs.

cache

Manage the shared build artifact cache.

install

Install packages defined in the project.

--watch, -w

Rebuild continuously on file changes.

--force

Force rebuild of all targets.

--verbose

Display full command lines of executed programs.

CONFIGURATION

dune

Per-directory build configuration files using S-expression syntax defining libraries, executables, and tests.

dune-project

Project-level configuration at repository root specifying project metadata and language version.

dune-workspace

Optional workspace configuration for multi-context builds and advanced project settings.

DUNE FILE EXAMPLE

$ (library
(name mylib)
(libraries str unix))

(executable
(name main)
(libraries mylib))

(test
(name test_mylib)
(libraries mylib alcotest))

CAVEATS

Requires OCaml or Reason compiler. Build artifacts go in the _build directory. Dune files use S-expression syntax, not YAML or TOML. Package management requires opam.

HISTORY

Dune was originally called jbuilder, created by Jane Street in 2016. It was renamed to Dune in 2018 and became the de facto standard build system for the OCaml ecosystem. The project aims to provide a modern, fast, and user-friendly build experience.