env-args

Useful when deploying programs where passing environment variables is more convenient and more secure than passing arguments to the process.

Add to your stack.yaml:

- github: chrisdone/env-args
  commit: bfcad7b70c217218fd512bf8dbd90bead51e9385

And in your app/main.hs:

import System.EnvArgs

Wrap withEnvArgs "YOURPREFIX_" around your arguments parser (e.g. optparse-applicative), and now you can pass

• YOURPREFIX_arg1=blah for --arg1 blah (drops the prefix and adds --).
• YOURPREFIX_arg_foo for --arg-foo (replaces _ with -)
• YOURPREFIX_ARG_FOO for --arg-foo (auto-lower-casing)