incrontab howto – filesystem status change notify

1. Install incrontab.

2. Edit /etc/incron.allow


3. Use incrontab command

<path> <mask> <command>
IN_ACCESS File was accessed (read) (*)
IN_ATTRIB Metadata changed (permissions, timestamps, extended attributes, etc.) (*)
IN_CLOSE_WRITE File opened for writing was closed (*)
IN_CLOSE_NOWRITE File not opened for writing was closed (*)
IN_CREATE File/directory created in watched directory (*)
IN_DELETE File/directory deleted from watched directory (*)
IN_DELETE_SELF Watched file/directory was itself deleted
IN_MODIFY File was modified (*)
IN_MOVE_SELF Watched file/directory was itself moved
IN_MOVED_FROM File moved out of watched directory (*)
IN_MOVED_TO File moved into watched directory (*)
IN_OPEN File was opened (*)

When monitoring a directory, the events marked with an asterisk (*) above can occur for files in the directory, in which case the name field in the returned event data identifies the name of the file within the directory.

The IN_ALL_EVENTS symbol is defined as a bit mask of all of the above events. Two additional convenience symbols are IN_MOVE, which is a combination of IN_MOVED_FROM and IN_MOVED_TO, and IN_CLOSE which combines IN_CLOSE_WRITE and IN_CLOSE_NOWRITE.

The following further symbols can be specified in the mask:
IN_DONT_FOLLOW Don't dereference pathname if it is a symbolic link
IN_ONESHOT Monitor pathname for only one event

IN_ONLYDIR Only watch pathname if it is a directory

Additionaly, there is a symbol which doesn't appear in the inotify symbol set. It it IN_NO_LOOP. This symbol disables monitoring events until the current one is completely handled (until its child process exits). 
Command translation

$$   dollar sign
$@   watched filesystem path (see above)
$#   event-related file name
$%   event flags (textually)
$&   event flags (numerically)
# incrontab -l
# incrontab -e
/var/www IN_ACCESS echo "/var/www/ wass accessed at $$date"

Access your web server in a browser and watch the status change.
# tail /var/log/syslog