View Source FileSystem

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An Elixir file change watcher wrapper based on FS, the native file system listener.

System Support

On MacOS 10.14, to compile mac_listener, run:

open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg

Usage

Add file_system to the deps of your mix.exs

defmodule MyApp.Mixfile do
  use Mix.Project

  def project do
  ...
  end

  defp deps do
    [
      {:file_system, "~> 1.0", only: :test},
    ]
  end
  ...
end

Subscription API

You can spawn a worker and subscribe to events from it:

{:ok, pid} = FileSystem.start_link(dirs: ["/path/to/some/files"])
FileSystem.subscribe(pid)

or

{:ok, pid} = FileSystem.start_link(dirs: ["/path/to/some/files"], name: :my_monitor_name)
FileSystem.subscribe(:my_monitor_name)

The pid you subscribed from will now receive messages like:

{:file_event, worker_pid, {file_path, events}}

and

{:file_event, worker_pid, :stop}

Example Using GenServer 

defmodule Watcher do
  use GenServer

  def start_link(args) do
    GenServer.start_link(__MODULE__, args)
  end

  def init(args) do
    {:ok, watcher_pid} = FileSystem.start_link(args)
    FileSystem.subscribe(watcher_pid)
    {:ok, %{watcher_pid: watcher_pid}}
  end

  def handle_info({:file_event, watcher_pid, {path, events}}, %{watcher_pid: watcher_pid} = state) do
    # Your own logic for path and events
    {:noreply, state}
  end

  def handle_info({:file_event, watcher_pid, :stop}, %{watcher_pid: watcher_pid} = state) do
    # Your own logic when monitor stop
    {:noreply, state}
  end
end

Backend Options

For each platform, you can pass extra options to the underlying listener process.

Each backend supports different extra options, check backend module documentation for more details.

Here is an example to get instant notifications on file changes for MacOS:

FileSystem.start_link(dirs: ["/path/to/some/files"], latency: 0, watch_root: true)