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How to Solve macOS File Sync Loop Caused by Folder Automation Scripts — The Folder Action Throttle Fix Shared on Reddit

If you’ve set up your Mac to automatically run scripts when files are added to a folder, you’re not alone. Folder Actions are a powerful part of macOS automation. But sometimes, these automations can go a little… wild. Especially when they end up triggering themselves over and over, causing an endless loop of syncing, scripting, syncing again, and repeat.

TLDR:

If you’re facing a never-ending file sync loop on macOS due to Folder Actions or automation scripts, you’re likely hitting a common pitfall. The script re-triggers itself because the synced folder is being changed — by the script. A fix shared on Reddit involves adding a time-based throttle to pause rapid re-execution. It’s a simple tweak that stops the chaos while still keeping your automation working.

What’s Going On?

Imagine this: you’ve got a folder on your desktop. Every time a file is added, a script compresses it into a ZIP and moves it to another folder (maybe synced to iCloud or Google Drive). Sounds smart, right?

But then… the move itself changes the folder. Which triggers the script. Which compresses again. Which updates the folder again. And now you’ve got a loop. Like a dog chasing its tail. Forever.

The Sync Spiral of Doom

This loop can cause several problems:

  • CPU revving like a jet engine 🚀
  • Mac fans going full-blast ❄️
  • Duplicate files piling up
  • Your cloud storage syncing forever

So what causes it? It’s the combo of:

  1. macOS Folder Actions
  2. Syncing services like iCloud Drive, Dropbox, or OneDrive
  3. An automation script that touches files in the watched folder

Yup. That’s all it takes to break the loop of sanity.

The Reddit Lightbulb Moment 💡

A clever user on Reddit finally cracked the code. The fix? Don’t stop automation. Just… slow it down. Add a throttle.

Here’s the key idea: add a short delay between each run of the script. If the script just ran, and another event comes in TOO SOON, ignore it. Easy, right?

The Simple Throttle Fix

You’re about to meet your new best friend: the timestamp file.

This file keeps track of the last time your script ran. Before running again, the script checks this timestamp. If it’s been less than, say, 10 seconds… it bails out.

Step-by-Step Guide:

Step 1: Create a hidden file to store the last-run time.


touch ~/.folderaction-last-run

Step 2: Edit your script and add the throttle logic:


#!/bin/bash

# Path to your timestamp file
TIMESTAMP_FILE="$HOME/.folderaction-last-run"

# How many seconds to wait between runs?
THROTTLE_SECONDS=10

# Get current and last run time
NOW=$(date +%s)
LAST=$(cat "$TIMESTAMP_FILE" 2>/dev/null || echo 0)
DIFF=$(($NOW - $LAST))

# Exit if it's too soon
if [ "$DIFF" -lt "$THROTTLE_SECONDS" ]; then
  echo "Throttled. Last run was $DIFF seconds ago."
  exit 0
fi

# Update timestamp
echo "$NOW" > "$TIMESTAMP_FILE"

# Your actual script commands go below
# e.g., compress, move, notify, etc.
echo "Running script!"
# Example:
# zip /path/to/output.zip /path/to/watched_folder/*

Step 3: Save and set executable permissions:


chmod +x /path/to/your/script.sh

Bringing It Back into Automator

If you’re using Automator’s Folder Actions, point the folder to your modified shell script. Here’s how to do it:

  1. Open Automator.
  2. Choose Folder Action as the document type.
  3. At the top, select the folder you want to watch.
  4. From the actions list, drag “Run Shell Script” into the workspace.
  5. Paste in the throttle-enabled script.
  6. Save it and test!

Why It Works

The script keeps a mental note (okay, digital note). It doesn’t allow itself to run unless it’s been long enough since the last run. It’s like a cool-down timer in a video game.

This stops the loop, preserves your CPU, and keeps your files from going into a quantum duplication state.

Bonus Pro Tips

  • Use Logging: Add echo statements or write logs to a file to see what’s happening behind the scenes.
  • Debug Carefully: Print the time values so you know if your script is getting throttled.
  • Don’t Throttle Too Hard: Keep the delay short enough that regular use doesn’t feel sluggish. 10–20 seconds is a good range.

Good to Know: Other Ways to Break the Loop

If you don’t want a throttle, here are some other options:

  • Move modified files to a different folder — so the watched folder isn’t affected again.
  • Turn off cloud syncing on the watched folder if possible.
  • Tag files after processing and ignore already-tagged files in the script.

But honestly? Throttling is the cleanest, simplest solution.

Reddit to the Rescue

Kudos to the Mac Reddit community for unburying this simple fix that Apple never explained. Sometimes you don’t need a fancy tool, just a basic shell script and a bit of logic.

The fix works whether you’re zipping files, transcoding videos, or even speaking notifications aloud with say, your Mac’s text-to-speech tool. It’s automation — with manners.

Wrapping It Up 💻

If your folder actions are stuck in an infinite loop, don’t panic. Just give them a breather. A tiny script can stop the madness and let your Mac breathe easy.

So go ahead. Automate boldly—but gently. And remember: even scripts need a timeout every now and then.