Elixir-script template for the commandline.

shell.exs

#!/usr/bin/env elixir
#
# A Template for writing an Elixir script to be used on the
# command-line.
#
# (c) 2019 by Andreas Altendorfer <[email protected]>
# License: Free to use without any warranty.
#
# Usage:
#   1. Add your command to strict and aliases on @opts
#   2. Implement your function (rename my_script() )
#   3. Call your script in `run()` (line 38)
#
defmodule Shell do
  alias IO.{ANSI}

  #
  # Add your script here
  #
  @opts [
    strict: [
      cmd: :string,
      my_cmd: :string
    ],
    aliases: [
      c: :cmd,
      m: :my_cmd
    ]
  ]

  def my_script(str, _args) do
    str |> String.upcase()
  end

  #
  # Call your script here
  #
  def run(args) do
    args
    |> case do
      {[cmd: cmd], args} -> system(cmd, args)
      {[my_cmd: cmd], args} -> my_script(cmd, args)
      _ -> no_command()
    end
  end

  # Default 
  def no_command(), do: red("ERROR: No command")

  # Example: Execute a system command. e.g. `-c ls`
  def system(cmd, args) do
    {result, _err} = System.cmd(cmd, args)

    [blue(cmd), red(inspect(args)), green(result |> String.trim())]
    |> Enum.join("\n")
  end

  def main(args) do
    OptionParser.parse!(args, @opts)
    |> run
  end

  defp blue(str), do: [ANSI.blue(), str, ANSI.reset()] |> Enum.join()
  defp green(str), do: [ANSI.green(), str, ANSI.reset()] |> Enum.join()
  defp red(str), do: [ANSI.red(), str, ANSI.reset()] |> Enum.join()
end

#
# MAIN
#
System.argv()
|> Shell.main()
|> IO.puts()