Introduction
The command line is the preferred way to create and interact with Elixir applications, inspect running systems, and prototype ideas.
Interactive Elixir (IEx) allows immediate evaluation of any expression, and it is also possible to define modules directly without saving them previously on a file. Similar tools exist in other programming languages; Ruby's IRB or Clojure's REPL are some examples.
Mix is a build tool that provides several tasks to create, compile, and test projects, and handle dependencies. It is also possible to define custom tasks with Mix. In the Creating custom Mix tasks recipe, we will create a task to display the memory usage. It is common for some applications to define their own tasks. Phoenix framework (which will be covered in Chapter 7, Cowboy and Phoenix) is just one example of this.
