monitor-file.js

#!/usr/bin/gjs
const Lang = imports.lang;
const GLib = imports.gi.GLib;
const Gio = imports.gi.Gio;

let file = Gio.file_new_for_path(ARGV[0]);
let monitor = file.monitor_file(Gio.FileMonitorFlags.WATCH_HARD_LINKS, null);
monitor.connect('changed', (monitor, file, otherfile, ev, data) => {
  log('file changed with event ' + ev);
});

let main_loop = new GLib.MainLoop(null, false);
main_loop.run();