Portable Nix/Ruby Web Server

server.rb

#! /usr/bin/env nix-shell
#! nix-shell -i ruby -p ruby bundler --pure
#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-20.03.tar.gz

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem 'sinatra'
  gem 'thin'
  gem 'haml'
end

get '/' do
  haml :index
end

Sinatra::Application.run!

__END__

@@ index
%h1
  Hello World

@@ layout
%html
  %head
    %title= "My app"
  %body
    = yield