MacOS – Monitor Folder Contents with launchd – Including Subfolders

launchdmacosscript

I want to make a shell script that runs any time the contents of a particular folder on my server are changed. Seems easy enough at first, because launchd has a directive called WatchPaths which triggers your script any time the contents of a folder change.

HOWEVER WatchPaths is not triggered by changes in subfolders. The folder I'm trying to watch is a few hundred MB of small web files, nested several levels deep in sub folders. Far too many folders to try to manually list each one.

Is there some other sane way to accomplish this?

Best Answer

WatchPaths doesn't appear to be able to watch a sub-directory recursively, so the best you can do with it is watch a single directory's activities. You might want to take a look at Folder Actions, they're discussed in detail in this blog post titled: Setup OS X Folder Actions to Know When a File is Added as well.

Another alternative is to use a CLI tool that's available in Homebrew via the brew install fswatch command. fswatch is a cross platform implementation that works on most flavors of *NIX includes macOS.

The FSEvents monitor, available only on OS X, has no known limitations, and scales very well with the number of files being observed.

Example

Here I've created a sub-directory called ~/somedir. I then invoked `fswatch against this directory:

$ mkdir ~/somedir
$ fswatch /some/dir

Now if we start adding files and sub-directories fswatch will notify:

$ touch ~/somedir/afile
fwatch msg>> /Users/joeuser/somedir/afile

$ mkdir ~/somedir/anotherdir
fswatch msg>> /Users/joeuser/somedir/anotherdir

$ touch ~/somedir/anotherdir/afile
fswatch msg>> /Users/joeuser/somedir/anotherdir/afile

The above can be adapted for use in a shell script which can take whatever other actions you require when any changes are detected against the directory tree that fswatch is monitoring.

Other Examples

To act on file system activity you can use one of these 2 patterns:

$ fswatch -0 path | while read -d "" event \
  do \
    // do something with ${event}
  done

Or this:

$ fswatch -o path | xargs -n1 -I{} program

References

Related Solutions

MacOS – Automatically Mount a Network Drive and Copy a File to a Network Folder (AppleScript)

Copying of files in Applescript is best done either through System Events or Finder, using the duplicate … to command, i.e.

tell application "System Events" to duplicate sourceFile to targetFolder

where both sourceFile and targetFolder need to be the correct object type for the application used – meaning disk item or finder item (both objects can be created from AppleScript alias objects, or textual path values with a bit of type coercion – I’d add the details, but you have not stated how the paths to both are stored / acquired in your script).

A few notes on your code:

There is no need to use globals when you have defined them as properties already. AppleScript properties are script scoped and persist across execution – they are only reset when the script is recompiled. If you assign those that need user setting missing value when declaring, you can even check if they are already set and skip re-prompting the user (there would be an even more comfortable and secure solution if Apple hadn’t deprecated Keychain Access Scripting).
There is no need for the repeated assignments and recursive call in your connectToServer() handler. The following code
```
set timeOutCounter to 0
repeat while (list disks) does not contain serverName and timeOutCounter is less than timeOutInterval
    -- mount drive
    delay someInterval -- recommended, so you don’t hectically loop
    set timeOutCounter to timeOutCounter + someInterval -- time out loop 
end repeat
```
will try to connect in the interval defined by someInterval, until the mount is available or timeOutIntervalis reached (assuming these values are declared. As properties, best – see above).
You might also want to offer your user a more comfortable way of selecting the target folder than typing a folder name from memory. Check out Standard Additions’s AppleScript dictionary for the choose folder command.
Finally, but that is mainly a matter of taste and coding style, I’d rather move the display dialog command into its own handler and call that, if needed repeatedly, from the script body, than use a C style mainLoop handler. I’ve found that, generally speaking, AppleScript runs out of Stack space easily when recursing and can get very confused about variable assignments, so it is a good idea to avoid recursive constructs where they are not necessary.

How force launchd not to look into subfolders with QueueDirectories parameter in launchd.plist

QueueDirectories won't work anyway, because it'd trigger on the subdirectories themselves whether or not they had any files in them. The mere existence of subdirectories in the watched directories will trigger the script.

Instead, you should use WatchPaths on the main directory itself -- whenever a new image file is added to the directory, the directory is modified, so WatchPaths will trigger your script to process the file. Moving the image file will modify the directory again, but since it happens while your script is running it won't trigger a rerun.