我是Elixir的新手，我正在尝试运行iex。当我输入＆＃39; iex＆＃39;在命令行中，我收到以下错误：
Erlang/OTP 20 [erts-9.0.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async->threads:10] [hipe] [kernel-poll:false] [dtrace]
** (Mix) "mix" with no arguments must be executed in a directory with a >mix.exs file
Usage: mix [task]
Examples:
mix - Invokes the default task (current: "mix run")
mix new PATH - Creates a new Elixir project at the given path
mix help - Lists all available tasks
mix help TASK - Prints documentation for a given task
我目前正在使用Elixir 1.5.1 / Erlang 20
为什么Elixir需要一个mix.exs文件才能运行shell？