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Ævar Arnfjörð Bjarmason


App::Inotify::Hookable - blocking command-line interface to inotify


Watch a directory, tell us when things change in it:

    inotify-hookable --watch-directories /tmp/watch-this

Watch a git tree, some configs, and a repository of static assets, restart the webserver or compress those assets if anything changes:

    inotify-hookable \
        --watch-directories /etc/uwsgi \
        --watch-directories /git_tree/central \
        --watch-directories /etc/app-config \
        --watch-directories /git_tree/static_assets \
        --on-modify-path-command "^(/etc/uwsgi|/git_tree/central|/etc/app-config)=sudo /etc/init.d/uwsgi restart" \
        --on-modify-path-command "^/git_tree/static_assets=(cd /git_tree/static_assets && compress_static_assets)"

Or watch specific files:

    inotify-hookable \
        --watch-files /var/www/cgi-bin/mod_perl_handler \
        --on-modify-command "apachectl restart"


This simple command-line program is my replacement for the functionality offered by Plack's Filesys::Notify::Simple. I found that on very large git trees Plack would spend an inordinate amount watching the filesystem for changes.

This program uses Linux::Inotify2, so the kernel will notify it instantly when something changes (actually it's so fast that we have to work around how fast it sends us events).

The result is that you can run this e.g. in a screen session and have it watch your development environment, and your webserver will have begun restarting before your finger leaves the save button.

vim and emacs temporary files are ignored by default (see --ignore-paths.) so you can edit your files without your server restarting unnecessarily.

Currently the command-line interface for this is the only one that really makes sense, this module is entirely blocking (although it could probably run in another process via POE or something). Patches welcome.


Note that boolean options can be negated with --no-OPTION, e.g. --no-r or --no-recursive to turn off the --recursive option which is on by default.

-w or --watch-directories

Specify this to watch a directory, you can give this however many times you like to watch lots of directories.

-f or --watch-files

Watch a file, specify multiple times for multiple files. You can watch files and directories in the same command.

-r or --recursive

If you supply this any directory you give will be recursively watched. This is on by default.

-c or --on-modify-command

A command that will be run when something is modified.

-C or --on-modify-path-command

A key-value pair where the key is a regex that'll be matched against a modified path, and the value is a command that'll be run. See the "SYNOPSIS" for an example.

Useful for e.g. restarting a webserver if you modify directory A but compressing some static assets if you modify directory B.

-t or --buffer-time

Linux will send you inotify events really fast, so fast that if you run something like:

    touch foo bar

You might get an event for foo in one batch, followed by an event for bar later on.

To deal with this we enter a loop when we start getting events and sleep for a default of 100 microseconds, as long as we keep getting events we keep sleeping for 100 microseconds, but as soon as we haven't received anything new we fire off our event handlers.

-i or --ignore-paths

Regexes for files/directories to ignore events for. By default this is set to regexes for vim and emacs temporary files, qr{\..*sw.\z} and qr{\.\#[^/]+\z} respectively.

The regexes match after any / in the path or the beginning of the string.

-d or --debug

Spew out some verbose debug output while running.


This module was originally developed at and for Booking.com. With approval from Booking.com, this module was generalized and put on CPAN, for which the authors would like to express their gratitude.


Ævar Arnfjörð Bjarmason <avar@cpan.org>