hazel-newvolume

A shell script to work with Hazel to automatically install apps on OS X.

The "Problem"

Many Mac apps come in ".dmg" files, and require the same set of steps:

1. Mount the .dmg (which will then appear in /Volumes/SomeNameHere/)

2. Find the .app inside the /Volumes/SomeNameHere/

3. Copy the .app from /Volumes/SomeNameHere/ to /Applications/

4. Say "yes" when asked if you want to replace it

5. Wait for the install to finish

6. Eject the .dmg

One Solution

Most of those steps can be automated, but there are some details which need to be considered:

1. How can you tell if a new volume is a DMG?

2. Assuming it is determined to be a DMG, how do you identify what needs to be installed? There are several possibilities, the first two is the most likely, but the others need to be considered:

   • There is one .app which needs to be copied to /Applications/. (This is the most common situation.)

   • it is a .pkg file which needs to be installed (second most common)

   • There is one .app but it is an installer (iTunes, Default Folder X, etc)

   • it is a prefPane which needs to be installed either to ~/Library/PreferencePanes/ or /Library/PreferencePanes/

   • there may be an .app and a .pkg file (MakeMKV)

   • there may be more than one app in the .dmg (for example: MailMate's DMG also includes SpamSieve)

   • there may be more than one app and more than one pkg

3. Once we have determined what needs to be installed, there are more considerations to make:

   • Is the app already installed?

     • is it currently running?

     • does it have any 'helper' apps that are running?

     • if the app or any of its helper apps are running, can they be quit safely (or at least, relatively safely)?

   • Is the version we are considering installing newer than the currently installed version?

     • if no, does that mean we should stop the installation or just inform the user, who might want to replace a newer, buggier version of an app with an older version? (Our answer may depend somewhat on what we do with apps that are already installed.)

4. {Other?}

Version 0.01 (2014-01-01)

To start with I decided to only deal with the most common scenario: a DMG is mounted and it has an app which is not an installer.

The script will be called via Hazel. Choose /Volumes/ as the Folder and then create a new rule using the "+" under “Rules”:

This is the rule that I created:

"Dated Added" "is after" "Date Last Matched" means that it will run once for every new item added to /Volumes/ (so the script will need to be smart enough to tell when it is not being used on a dmg).

The two Display Notifications are mostly for debugging purposes, so I can tell when the recipe has started and finished.

Faux Hazel Syncing

Hazel doesn't sync its rules across Macs, but you can sort of fake it when you are creating a rule which points to a shell script on Dropbox.

• Create the rule on one Mac, including the "Run Shell Script" part. Instead of using an embedded script, use an external script file which is saved on Dropbox. The full path to hazel-newvolume.sh is /Users/luomat/Dropbox/bin/hazel-newvolume.sh on all of my Macs which sync via Dropbox. You can put it wherever you want in your Dropbox, as long as the paths are the same on all of your Macs. (Note: on one computer which does not have enough internal storage for my Dropbox, I told the Dropbox.app to put its folder on /Volumes/External/Dropbox but then I linked it to /Users/luomat/Dropbox/ .)

• Click the gear icon in Hazel and Export "Volumes" rules from Hazel. (see image) I'd suggest putting the Volumes.hazelrules file in Dropbox to make it easier to import on your other Macs.

• On the other Macs, make sure you have an entry for /Volumes/ under Folders. You can then import the Volumes.hazelrules file by either: a) using the same 'gear' menu in the above image (choose "Import Rules…"), or b) drag the Volumes.hazelrules file to the /Volumes/ item under "Folders" or c) simply double-click the Volumes.hazelrules file and choose to import it into Volumes:

Once I have exported this Hazel rule on one Mac and imported it on the other Mac(s), any changes I make to the hazel-newvolume.sh script will be reflected on all of the computers which sync via Dropbox.