Merge pull request #9 from thbar/custom-listener-args

Support optional listener args

README.md

@@ -60,6 +60,18 @@ Execute in iex
 iex > Monitor.start
 ```
 
+## Tweaking behaviour via listener extra arguments
+
+For each platform, you can pass extra arguments to the underlying listener process via the `listener_extra_args` option.
+
+Here is an example to get instant notifications on file changes for Mac OS X:
+
+```elixir
+use ExFSWatch, dirs: ["/tmp/fswatch"], listener_extra_args: "--latency=0.0"
+```
+
+See the [fs source](https://github.com/synrc/fs/tree/master/c_src) for more details.
+
 ## List Events from Backend
 
 ```shell

lib/exfswatch.ex

 require Logger
 
 defmodule ExFSWatch do
-  defmacro __using__([dirs: dirs]) do
+  defmacro __using__(options) do
     quote do
-      def __dirs__, do: unquote(dirs)
+      def __dirs__, do: unquote(Keyword.fetch!(options, :dirs))
+      def __listener_extra_args__, do: unquote(Keyword.get(options, :listener_extra_args, ''))
       def start,    do: ExFSWatch.Supervisor.start_child __MODULE__
     end
   end

lib/exfswatch/worker.ex

@@ -9,7 +9,7 @@ defmodule ExFSWatch.Worker do
 
   def init(module) do
     backend = ExFSWatch.backend
-    port = start_port(backend, module.__dirs__)
+    port = start_port(backend, module.__dirs__, module.__listener_extra_args__)
     {:ok, %__MODULE__{port: port, backend: backend, module: module}}
   end
 
@@ -29,15 +29,16 @@ defmodule ExFSWatch.Worker do
   end
 
 
-  defp start_port(:fsevents, path) do
+  defp start_port(:fsevents, path, listener_extra_args) do
     path = path |> format_path
+    args = [ listener_extra_args, '-F' | path]
     Port.open({:spawn_executable, :fsevents.find_executable()},
-              [:stream, :exit_status, {:line, 16384}, {:args, ['-F' | path]}, {:cd, System.tmp_dir!}]
+              [:stream, :exit_status, {:line, 16384}, {:args, args}, {:cd, System.tmp_dir!}]
     )
   end
-  defp start_port(:inotifywait, path) do
+  defp start_port(:inotifywait, path, listener_extra_args) do
     path = path |> format_path
-    args = [ '-c', 'inotifywait $0 $@ & PID=$!; read a; kill $PID',
+    args = [ listener_extra_args, '-c', 'inotifywait $0 $@ & PID=$!; read a; kill $PID',
              '-m', '-e', 'close_write', '-e', 'moved_to', '-e', 'create', '-e',
              'delete_self', '-e', 'delete', '-r' | path
            ]
@@ -45,9 +46,9 @@ defmodule ExFSWatch.Worker do
               [:stream, :exit_status, {:line, 16384}, {:args, args}, {:cd, System.tmp_dir!}]
     )
   end
-  defp start_port(:"inotifywait_win32", path) do
+  defp start_port(:"inotifywait_win32", path, listener_extra_args) do
     path = path |> format_path
-    args = ['-m', '-r' | path]
+    args = [ listener_extra_args, '-m', '-r' | path]
     Port.open({:spawn_executable, :"inotifywait_win32".find_executable()},
               [:stream, :exit_status, {:line, 16384}, {:args, args}, {:cd, System.tmp_dir!}]
     )