It's Magix

Long time no see! In this post I would like to present Magix, a tool to build, cache, and run possibly compiled scripts with dependencies using the Nix package manager.

First, I would like to draw your attention to a blog post by Brian Hicks, in which he introduces nix-script. In brief, Magix is a slimmed down version of nix-script:

• Magix is simple and stupid.
• Magix is a tiny wrapper around nix-build.
• Magix uses Nix derivation templates, and so, is easier to understand, modify, and enhance.
• Magix is heavily tested (only unit tests at the moment, but please drop a pull request).

Have a look at the following example:

#!/usr/bin/env magix
#!magix haskell
#!haskellPackages text

import Data.Text (pack)
import Data.Text.IO (putStrLn)
import Prelude hiding (putStrLn)

main :: IO ()
main = putStrLn $ pack "Hello, World!"

Magix is going to

1. parse the directives,
2. assemble a tiny Nix wrapper expression,
3. use the Nix package manager to build this expression, and
4. run the derivation result.

The first time doing so, takes around 0.9 seconds on my machine. That sucks. However, in step 1, Magix also hashes the input script, and saves a link to the derivation result. That is, if Magix knows a script, the next execution is much faster: 0.09 seconds. That is one order of magnitude faster!