Is there there a way to check a folder/file for changes (includes adding files, deleting files, changes in files,...). The 'Folder action' in Automator is only checking if any files are newly added.
You can add a "Run Shell Script" action with the command:
find <directory> -newermm <reference_file>
This will give you all files and directories inside
<directory> that have changed since the last change of
<reference_file>. Just make sure you modify the
<reference_file> each time you run the Automator script.
Also give a look to the find manual page (enter
man find in the terminal) for more options. Find is very powerful and further refining your search is usually a matter of a couple of additional options. E.g. to search only for directories modified after
find <directory> -type d -newermm <reference_file>
If the version that ships with OSX is not enough, you can also try the version that comes with
findutils (brew, macports etc) which should have slightly more features.
So last time I checked, Automater is using Applescript in the background to script your actions. Applescript does not have much depth to it. While it can get the list of files in a directory (and so therefore you could find out when something gets deleted), I don't believe it can calculate changes to a file.
What you really need to harness is file system notifications. And since that's a beast, I would take kraymer's advice and use launchd. It has hooks to execute anytime the contents of a folder is changed. Lingon (see also its outdated SourceForge page) is a great application for helping people jump into launchd. You can write your automator script/application to do whatever you were planning to do when your directory was modified and just have the launchd task call that.
You can check at an earlier answer of mine, but it sounds like you want
fs_usage -f filesys
Launchd is not the way to go for file changes, fs_usage uses the underlying machine that powers spotlight.
EDIT: I'm utterly wrong here. Launchd has exactly that functionality required, ie: do something on a file or directory change.
You make a .plist file.
Scream "XML SUX FOR CONF FILES!" ( It really does. )
and you'll want to use one or both of the keys below in your launchd job.
WatchPaths <array of strings> This optional key causes the job to be started if any one of the listed paths are modified. QueueDirectories <array of strings> Much like the WatchPaths option, this key will watch the paths for modi- fications. The difference being that the job will only be started if the path is a directory and the directory is not empty.