Aliases are build targets that do not correspond to specific files. For example, the runtest alias corresponds to running tests.

Model and Syntax

Dependencies and actions can be attached to an alias. When this alias is requested to be built, these dependencies are built and these actions are executed. Aliases are attached to specific directories.

In commands such as dune build, the syntax to refer to the x alias is @x, for example dune build @x. This is why it is common to refer to it as “the @x alias”, or “attaching a rule to @x”.

Building @x will build x in all subdirectories of the current directory. This is the most common case, but it is possible to restrict this using different syntaxes:

  • @sub/dir/x will build x in sub/dir and its subdirectories.

  • @@x will build x in the current directory only.

  • @@sub/dir/x will build x in sub/dir only.

If dir is the directory of a build context, it restricts the alias to this context.

To summarize, the syntax is:

  • @ (recursive) or @@ (non-recursive): determine if subdirectories are included

  • optional build context root: restrict to a particular build context

  • optional directory: only consider this subdirectory

  • alias name


  • dune build @_build/foo/runtest only runs the tests for the foo build context

  • dune build @runtest will run the tests for all build contexts

User-Defined Aliases

It is possible to use any name for alias names; it will then be available on the command line. For example, if a Dune file contains the following, then dune build @deploy will execute that command.

 (alias deploy)
 (action ./run-deployer.exe))

Built-In Aliases

Some aliases are defined and managed by Dune itself: