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more fun with Hammerspoon

For anyone using Hammerspoon and folder ‘watchers’ to alert them to changes to a given folder, I’ve updated the watcher function I wrote about here

The problem with the simple alert I demonstrated last time is that it only hangs around for a second or two (much less than a Folder Action alert, which takes a couple of minutes to time out). In this updated function, it now also writes a list of the file changes to a (by default) file on the Desktop. The write is an append: if the file doesn’t exist it will create it before writing; if it does exist, it will append the latest changes and date to the file. This way, even if you miss the alert, you’ll always have a record of what files have been added, deleted or modified in your watched folder.

In this example, the folder being watched is ~/Library/LaunchAgents since we want to be aware of any adware, malware or other unsavoury processes being surreptitiously added by, for example, apps we download from the internet. Although there are, of course, many legitimate reasons for apps placing items in here, this folder is prime real estate for attackers as it is one of the locations that can launch processes at log in time without the user’s interaction (or knowledge).

Here’s the code, also available from my pastebin here. A code walkthrough follows.

function writeStringToFileWithMode(aString, aPath, aMode)
local this_file
this_file =, aMode)

function myFolderWatch(files)
local str = "Launch Agents folder was modified on " .. .. " :\n\t"
local this_path = os.getenv("HOME") .. "/Desktop/LaunchFolderModified.txt"
local ignore = "DS_Store"
local count = 0

for _,file in pairs (files) do
count = count + 1
i = string.find(file, ignore)
if not i then
str = str .. file .. "\n\t"
if count == 1 then
str = "\n"
str = str .. "\n"
writeStringToFileWithMode(str, this_path, "a")

if string.len(str) > 2 then"Launch Agents folder was modified.")

local aWatcher ="HOME") .. "/Library/LaunchAgents/", myFolderWatch):start()

Code walkthrough
The first function, ‘writeStringToFileWithMode’ is just a convenience function. Hopefully the clue is in the name. The ‘aMode’ parameter is either “w” for write(over) or “a” for write(append).

The myFolderWatch function starts off by declaring some local variables.

‘str’ includes the initial line that we want to write to our output file and interpolates the time of the change by calling

‘this_path’ defines the path that we want to write our list of file names too.

The ‘ .. ‘ in both these assignments is a string concatenator (i.e., like ‘&’ in AppleScript or ‘stringByAppendingString’ in Obj-C).

‘ignore’ is a string that will help us to exclude .DS_Store files from triggering the alert or appearing in the list of file changes.

The ‘count’ variable is an internal var we need in order to eliminate .DS_Store changes when it’s the only change. Lua doesn’t have an easy way to count entries in tables, so we bascially iterate a variable each time through the loop to achieve the same effect.

After that, we have the ‘for’ loop. For loops in Lua are weird (at least for me), as you’ll see that they have this structure for a,b in pair (aPair). I won’t go into why, other than to say its a result of Lua’s table data structure. The '_' here is just a dummy variable for the first parameter. The ‘files’ in parentheses are the list of file names (not file specifiers, you AppleScripters!) that were added, deleted, or modified in the watched folder.

The loop begins by incrementing the count, then checks for the ignore file (.DS_Store). If the ignore file is not found, we then append the filename to the str variable.

If it is found, we check the count. If the count is ‘1’ (i.e., the only change was .DS_Store) we discard the entire str var and replace it with new line character. If the count is more than 1 we don’t do anything to ‘str’. We just ignore adding anything to it all.

At the end of the for loop we add another new line to the string just so our outputted text file looks nice and neat.

Then we call the write function mentioned above, passing ‘a’ (append) for the mode.

Finally, we fire the UI alert on the condition that the string has got more than 2 characters in it (if it didn’t it was just the “\n\n” string from ignoring the DS.Store file).

After the function definition, the aWatcher variable sets up the watcher on the path we want to observe and tells the watcher to start monitoring. It tells the watcher to call our myFolderWatch function when anything happens.

Deploying the code
After editing the config file, remember there’s two steps: i. save the file and ii. choose ‘Reload Config’ from the Hammerspoon menu.

Further Reading:
More details are available about Hammerspoon from the official site here.

My beginners guide with the original simple watcher function is here.


how to save and print email attachments

I was recently asked for a script that would automatically save and print all the pdfs from one particular client’s emails. Since this is quite a common use case (think invoices from a particular supplier, for example) and involves a fair bit of complexity, I thought I’d share the answer for any others out there that have the same need.

We’re going to need to do three things; install a script, set up a mail rule, and set up folder actions. Here we go!

Part 1: Install Script

Copy and paste the script you see below from here:

save mail attachmentsSave this script with a name like ‘CopyAttachments’ in

~/Library/Application Scripts/

(note: ~/Library means your user library. You can find it by triple-clicking the path above, then control-click on the highlighted text and choose Services > Reveal in Finder)

Part 2: Set up Mail Rule

Open Click on your Inbox in the sidebar. Click ‘Mail > Preferences… > Rules > Add Rule’

Under ‘Description’ give the rule a name (e.g., ‘Copy attachments’)

Set ‘If ANY of the following conditions are met’:


‘From contains’

and the email address of the person whose attachments you want to target.

(note: You can add more than one person’s email if you wish, but you do so by hitting the ‘+’ key and adding a new condition, not by adding more than one address in the text field. Each text field must contain only one condition, i.e., email address or keyword).

Next, set ‘Perform the following actions:’


‘Run AppleScript’

Click the ‘No Script Selected’ button and choose ‘CopyAttachments’

Click ‘OK” and in the following dialog click ‘Apply’.

3. Create & Set up a Folder Action

Open From the open panel choose ‘Folder Action’.

In the large, empty panel at the top you’ll see

‘Folder Action receives files and folders added to’ Choose folder

Click the Choose folder menu, choose Other. Select the folder you want the attachments to be saved in.

In the filter/search bar on the left of the Automator window, type ‘print images’. Drag the ‘Print Images’ selection from the results list into the middle of the empty workflow and release.

You can set some options here if you like (‘scale to fit’ might be useful).
You can choose either ‘Default Printer’ or click to select your actual printer. If your actual printer is the default, it won’t make any difference.

Press ‘command-S’ on your keyboard to save. Supply a name (e.g. Print PDFs) and hit ‘OK’. You do not choose a save location.

Quit Automator.

Open a Finder window and navigate to the folder where the attachments are going to be saved.

Hold down the ‘control’ key on your keyboard and click the attachments folder. From the contextual menu, go to Services > Folder Actions Setup… and click to open the dialog box.

Navigate down the list of scripts till you see the name of the Automator action you saved above and select it. Click ‘Attach’.

In the parent dialog box, check the box at the top that says ‘Enable Folder Actions’ and ensure that in the list on the left the attachments folder is listed and checked. Check that on the right, the ‘Print PDFs.workflow’ is checked.

If all is in order, close the dialog box. The procedure is complete and the workflow is installed.


It’d be wise to test the script as soon as possible. If it fails to work, double check that you’ve entered the correct path in the AppleScript as that’s the most likely point of failure. Let’s suppose your hard disk is called ‘Macintosh HD’, your user name is “Mack” and the folder you want to save the attachments in is “Invoices From Acme”, then the set attachmentsFolder line should look like this:

set attachmentsFolder to "Volumes:Macintosh HD:Users:Mack:Invoices From Acme:" as rich text

You must ensure you’ve already created the folder ‘Invoices From Acme’ before running the script. Also, be sure you don’t forget the trailing colon at the end of the path and that you have a matching pair of opening and closing quotes around the path name.

Any problems, drop me a comment below and I’ll try to help you out. Good luck and enjoy! 🙂

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