inotify-hookablep - Online in the Cloud

PROGRAM:

NAME

inotify-hookable - blocking command-line interface to inotify

SYNOPSIS

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"

DESCRIPTION

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.

OPTIONS

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.

ACKNOWLEDGMENT

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.

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