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Hey, an event driven file watcher for NodeJS with some sugar

Warning I: this project is in early development stage, you might not find it useful for now. It only works in Linux (2.6+) boxes (as it depends on libnotify to do most of the work).

Most of this lib is a wrapper around inotify with EventEmitter tied on.

Install from npm

$ npm install hey


var Hey = require('hey').Hey;
var watch = new Hey({
    path : '/path/to/something',
    recursive : true | false [,
    mask : Hey.FLAGS.DELETE | Hey.FLAGS... ]
watch.on('create', function(path, type, mask) {
    // do what you want 'cause a pirate is free ... 
watch.on('EOB', function() {
    console.log('arrr! ya arrr spyin\' ta manee scrrrrrolls per now!');



Hey constructor takes an object as parameter, and it contains the following keys:

  • path : the path to watch (required, obviously);
  • recursive : in the case the path you choose is a folder, you can choose to watch it recursively. Optional, default not set;
  • mask : the mask to listen to. Ex. if you want just to watch for new files, you use only Hey.FLAGS.CREATE as mask. All available masks (for Hey, not libnotify) are listed in this document; Optional, default to Hey.FLAGS.MODIFY | Hey.FLAGS.CREATE | Hey.FLAGS.DELETE | Hey.FLAGS.SELF_DELETE | Hey.FLAGS.MOVE | Hey.FLAGS.SELF_MOVE;

Warning II: activating recursive in a folder, you may run out of buffer (as it supports 1024 listeners). We do not plan to change this now as it required, on Linux, changing the ulimit fopen size and the source code of inotify.

Available events

The following events are available for use (but, most of them only works with folders):

  • EOB : fired when all available listeners are taken; perhaps you're watching too many files?
  • FB : fired when some listener becomes available; it means Free Buffer, not the social thing;
  • any : fired when any path event occurs (except EOB and FB);
  • access : fired when a file is accessed;
  • modify : fired when a file is modified;
  • open : fired when a file is opened;
  • close : fired when a file is closed;
  • metadata : fired when the path attributes are modified;
  • create : fired when a path is created;
  • delete : fired when a path is deleted;
  • self delete : fired when the path from constructor is deleted;
  • self move : fired when the path from constructor is moved;
  • move : fired when a path is moved;
  • ignore : fired when an event is ignored (this event could happen if you use your own mask);
  • unknown : fired when an unknown event happens to a path (not really unknown, but not relevant to the moment IMHO).


The callback function can receive three arguments:

  • path : the path which triggered the event;
  • type : fow now, if the path is a file Hey.FILE or directory Hey.DIRECTORY;
  • mask : the mask of the event (number).

Warning III: these parameters works for all events except for EOB and FB, which receives none.

Mask flags


Developer notes

I ran Hey in my home folder (ext4 fs) recursively, which have around 210G of data, around 41157 folders and 484730 files. When started, the CPU usage goes to ~30% (Core i7) and memory usage to ~180M. When the "first round" of processing is done (read the folder recursively), CPU usage goes to 0% and memory usage to ~80M; and I couldn't detect any leaks so far, as it's runtime was about 6 hours. Of course, more testing needs to be done, specially if the number of notifiers increase.

Note: using default inotify BUF_LEN and ulimit fopen in 1024.


Our plan is to support all platforms in the future, as Node's evolves (seriously, do this kind of work on what it is now would be insane).


  • better documentation of the source code;
  • a real document page, examples, and so on;
  • tests!
  • jsHint standards we don't like code standards.


Copyright (C) 2012 Humantech Gestao do Conhecimento

Distributed under the MIT License, the same as NodeJS.

Read this if you're in doubt.