inotify bindings for Erlang
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inotify bindings for Erlang

gen_inotify is an Erlang bindings library to inotify(7) Linux subsystem to watch filesystem events.

Usage example

1> application:start(gen_inotify).
2> file:make_dir("/tmp/watch").
3> {ok, H} = gen_inotify:open().
4> gen_inotify:add(H, "/tmp/watch", [if_dir, create, delete]).
5> file:make_dir("/tmp/watch/subdir").
6> file:del_dir("/tmp/watch/subdir").
7> flush().
Shell got {inotify,#Port<0.620>,"/tmp/watch/subdir",0,[is_dir,create]}
Shell got {inotify,#Port<0.620>,"/tmp/watch/subdir",0,[is_dir,delete]}

/proc interface

inotify has per-UID limits on number of sockets, events, and watches. These limits can be read and modified using /proc interface.

  • /proc/sys/fs/inotify/max_user_instances -- limit on number of open inotify descriptors
  • /proc/sys/fs/inotify/max_user_watches -- limit on total number of watched objects (files and directories) across the inotify descriptors
  • /proc/sys/fs/inotify/max_queued_events -- maximum number of unread filesystem events before a queue overflow message is generated and the events start being dropped

Details are described in inotify(7) man page.

Known limitations and problems

  • watching a directory recursively in a robust way is impossible (e.g. all open(2) events between subdirectory creation and adding it to inotify descriptor are lost), so "best effort" heuristic is used
  • file renames are not tracked by the port driver, thus messages about a file that got renamed carry the file's original path, and removing it from watching requires the original name as well
  • unicode characters in filenames are not supported


Linux kernel 2.6.36 or above and glibc 2.9 or above. These requirements are satisfied in Debian 7 Squeeze and CentOS 7.0.


gen_inotify is documented using EDoc. A local copy is generated with make doc command to ./doc/ directory. An already generated online copy is available at

Contact and license

gen_inotify library is written by Stanislaw Klekot . The primary distribution point is

gen_inotify library is distributed under 3-clause BSD license. See COPYING file for details.