Installation

The best method of installing Mill is to just install a bootstrap script. This script can determine the best version to be used by a project (e.g. by reading a .mill-version file) and will use this exact Mill version. If that version is not installed locally, it will be downloading for you.

Bootstrap Scripts

There are currently two bootstrap script available, one in the Mill repository, which only work for Linux and Unix-like machines, and one external millw script, with more features and also Windows support.

Using millw is recommended.

We plan to merge both script in the future.

Mill’s Bootstrap Script (Linux/OS-X Only)

If you are using Mill in a codebase, you can commit the bootstrap launcher as a ./mill script in the project folder:

curl -L https://github.com/com-lihaoyi/mill/releases/download/0.10.15/0.10.15 > mill && chmod +x mill

Now, anyone who wants to work with the project can simply use the ./mill script directly:

./mill version
./mill __.compile # double underscore

The mill command will automatically use the version specified by the bootstrap script, even if you installed it via other means. The ./mill file has a version number embedded within it, which you can update simply by editing the script. Note this only works for versions 0.5.0 and above.

Bootstrap scripts are also useful for running Mill in CI, ensuring that your Jenkins/Travis/etc. box has the correct version of Mill present to build/compile/test your code.

millw

Instead of installing Mill directly, you can also use lefou/millw as drop-in replacement for mill. It provides a small shell script and also a Windows batch file, that transparently downloads mill and executes it on your behalf. It respects various ways to configure the preferred Mill version (MILL_VERSION env var, .mill-version file, --mill-version option) and can also be used as a bootstrap script in your project.

Downloading Mill

OS X

Installation via homebrew:

brew install mill

Arch Linux

Arch Linux has a Community package for mill:

pacman -S mill

FreeBSD

Installation via pkg(8):

pkg install mill

Gentoo Linux

emerge dev-java/mill-bin

Windows

To get started, download Mill from Github releases, and save it as mill.bat.

If you’re using Scoop you can install Mill via

scoop install mill

WSL / MSYS2 / Cycgin / Git-Bash

Mill also works on "sh" environments on Windows (e.g., MSYS2, Cygwin, Git-Bash, WSL); to get started, follow the instructions in the Manual section. Note that:

In some environments (such as WSL), Mill might have to be run without a server (using -i, --interactive, --no-server, or --repl.)
On Cygwin, run the following after downloading mill:

sed -i '0,/-cp "\$0"/{s/-cp "\$0"/-cp `cygpath -w "\$0"`/}; 0,/-cp "\$0"/{s/-cp "\$0"/-cp `cygpath -w "\$0"`/}' /usr/local/bin/mill

Docker

You can download and run a "Docker image containing OpenJDK, Scala and Mill" using

docker pull nightscape/scala-mill
docker run -it nightscape/scala-mill

Manual

To get started, download Mill and install it into your HOME ".local/bin" via the following curl/chmod command:

sh -c "curl -L https://github.com/com-lihaoyi/mill/releases/download/0.10.15/0.10.15 > ~/.local/bin/mill && chmod +x ~/.local/bin/mill"

Coursier (unsupported)

Installing mill via coursier or cs is currently not officially supported. There are various issues, especially with interactive mode.

Updating Mill

If you have installed Mill via the recommended Bootstrap Script method, you don’t need to install multiple version of Mill explicitly.

Follow the next Overriding Mill Versions section for details.

Overriding Mill Versions

Apart from downloading and installing new versions of Mill globally, there are a few ways of selecting/updating your Mill version. This will only work, if you have choosen one of the Boostrap script methods:

Create a .mill-version file to specify the version of Mill you wish to use:

echo "0.5.0" > .mill-version

.mill-version takes precedence over the version of Mill specified in the ./mill script.

Pass in a MILL_VERSION environment variable, e.g.

MILL_VERSION=0.5.0-3-4faefb mill __.compile

MILL_VERSION=0.5.0-3-4faefb ./mill __.compile

to override the Mill version manually. This takes precedence over the version specified in ./mill or .mill-version

Automatic Mill updates

If your project is hosted on GitHub, GitLab, or Bitbucket, you can use Scala Steward to automatically open a pull request to update your Mill version (in .mill-version file), whenever there is a newer version available.

Scala Steward can also scan your project dependencies and keep them up-to-date.

Development Releases

In case you want to try out the latest features and improvements that are currently in the main branch, unstable versions of Mill are available as binaries named #.#.#-n-hash linked to the latest tag.

The easiest way to use a development release is to use one of the Bootstrap Scripts, which support Overriding Mill Versions via an MILL_VERSION environment variable or a .mill-version file.