Watches lib/ for source changes and automatically compiles + hot-pushes updated modules to all running Android and iOS devices.

Apps must already be running. Modules are loaded in place — no restart. Only modules that actually changed are pushed each cycle.

Press Ctrl-C to stop.

Options: --cookie Erlang cookie (default: mob_secret) --debounce ms to wait after a change before compiling (default: 300) --interval ms between file-change polls (default: 500)

Examples:

mix mob.watch
mix mob.watch --debounce 500
mix mob.watch --cookie my_cookie

Under the hood

mix mob.watch is an mtime-polling file watcher that drives mix compile and nl/1 in a loop:

# On startup:
writes OS PID → _build/mob_watch.pid    # used by mix mob.watch_stop

# Each cycle (every --interval ms):
snapshot mtimes of lib/**/*.ex
if any changed:
  :timer.sleep(debounce_ms)             # wait for format-on-save to settle
  System.cmd("mix", ["compile"])        # compile in a subprocess
  for each changed BEAM, on each node:
    :rpc.call(node, :code, :load_binary, [...])

Compile runs in a subprocess (not Mix.Task.run("compile")) so that Mix's task cache doesn't prevent recompilation on subsequent file saves.

The watch loop is equivalent to running mix compile && nl(ChangedModule) in a terminal after every save — mix mob.watch just does it automatically.