Help to eject or unmount disk upon shutdown

Question

Hello all,
Please take pity on a newbie and answer what I hope is a really simple script question. This is my first attempt at Apple Script.
I have searched for a script that will eject (unmount) a disk upon shutdown, but haven't found anything on this board. Do you have a reference to an archived script or an example of such code?
Background:
I have a new FireWire drive (Western Digital MyBook). It is OSX compatible, but not well integrated. For example, it should power off when I shut down the computer. It does so, but only if I unmount it first. If you have a similar drive, I should note that this behavior began when I reformatted it to HFS+ (Journaled) from the OEM FAT32. I would like to autmate the un-mounting upon shut-down via an Apple Script.
I am running OSX 10.3.9 on an E-Mac. As for my programming skills, I used to program in Fortran on both IBM and Unix mainframes, and do some basic Unix system administration tasks. So, I should be able to manage this scripting task if given the right advice.
Thanks in advance for your help!
E-Mac   Mac OS X (10.3.9)  
E-Mac   Mac OS X (10.3.9)  
E-Mac   Mac OS X (10.3.9)   Western Digital MyBook Firewire Drive

Answer 1

The issue isn't how to unmount the disk (that's the easy part), the problem is when to trigger it.
There is no standard mechanism for launching a script at shutdown, so there's no way to tell your script to run prior to the shutdown.
The best solution I can think of is a stay-open script that sits around doing nothing all day, until it quits. When it quits it unmounts the drive.
Under normal circumstances you wouldn't quit the script at all - just leave it running, but when the OS tells it to quit as part of the normal shutdown process it does its thing.
Here's one way of doing it:
on run
-- nothing to do here
end run
on idle
return 3600 -- do nothing, and dont' bother me again for an hour
end idle
on quit
tell application "Finder"
try
eject disk "diskName"
end try
end tell
continue quit
end quit
The 'run' handler is executed when the script is launched, but there's nothing we need to do there.
The 'idle' handler is run periodically in the background - again, we don't need to do anything here, either. The return value tells AppleScript how long to wait before re-running the idle handler
The 'quit' handler does the work - as soon as it's called it unmounts the drive, then continues with the normal quit process.
Of course, there's no checking here to make sure you really are shutting down (vs. just quitting the script manually), so you might want to add some validation (prompt the user, maybe?). You'll notice I wrapped the eject command in a try block - that way it'll fail silently if the disk isn't mounted, otherwise it would post an error dialog "Can't get disk "diskName"".