Example: Writing a Launch Agent for Apple’s launchd

Clutter in programmer workspaces, whether digital or physical, add a mental cost. An area of common clutter is the ~/Downloads directory in Mac OS X. I want to clean it up… programmatically.

The Goal

I want a background job to find files in ~/Downloads which haven’t been modified within the past week and move them into ~/.Trash. In zsh, we do:

mv ~/Downloads/*(mw+1) ~/.Trash

Read man zshexpn for more awesomeness on shell expansion.

Launch Agents

For a user-specific background job, Apple recomends creating a Launch Agent, which is a .plist XML file located in ~/Library/LaunchAgents.

~/Library/LaunchAgents/com.thoughtbot.cleandownloads.plist will run my script once an hour:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key>
  <string>com.thoughtbot.cleandownloads</string>
  <key>ProgramArguments</key>
  <array>
    <string>mv</string>
    <string>~/Downloads/*(mw+1) ~/.Trash</string>
  </array>
  <key>StartCalendarInterval</key>
  <dict>
    <key>Hour</key>
    <integer>1</integer>
  </dict>
</dict>
</plist>

Read Creating Launch Daemons and Agents for more on how to structure the .plist file.

Ain’t nobody dope as me, my Downloads directory is so fresh and so clean clean.