GenMagic

Determine file type. Elixir bindings for libmagic.

Installation

The package can be installed by adding gen_magic to your list of dependencies in mix.exs:

def deps do
  [
    {:gen_magic, "~> 0.20"}
  ]
end

Usage

The libmagic library requires a magic file which can be installed in various locations on your file system. A good way of locating it is given in the default config:

database = [
  "/usr/local/share/misc/magic.mgc",
  "/usr/share/file/magic.mgc",
  "/usr/share/misc/magic.mgc"
] |> Enum.find(&File.exists?/1)

The GenServer SHOULD be run under a supervisor or a pool as it is designed to end should it receive any unexpected error. Here we run it under a supervisor:

{:ok, _} = Supervisor.start_link([
  {GenMagic.ApprenticeServer,
  [database_patterns: [database], name: :gen_magic]}],
  strategy: :one_for_one)

Now we can ask it to inspect a file:

> GenMagic.ApprenticeServer.file(:gen_magic, Path.expand("~/.bash_history"))
{:ok, [mime_type: "text/plain", encoding: "us-ascii", content: "ASCII text"]}

For a one shot test, use the helper method:

> GenMagic.perform(Path.join(File.cwd!(), "Makefile"))

{:ok,
 [
   mime_type: "text/x-makefile",
   encoding: "us-ascii",
   content: "makefile script, ASCII text"
 ]}

Check uploaded files in a Phoenix controller

You can inspect the file from your controller:

def upload(conn, %{"upload" => %{path: path}}) do
  {:ok, [mime_type: _, encoding: _, content: content]} = GenMagic.ApprenticeServer.file(:gen_magic, path)
  text(conn, "Received your file containing #{content}")
end

Soak test

Run an endless cycle to prove that the GenServer is resilient:

find /usr/share/ -name *png | xargs mix run test/soak.exs
find . -name *ex | xargs mix run test/soak.exs

Acknowledgements

Original design, implementation and C code by Evadne Wu. Elixir wrapper by devstopfix.

License

TBC.