That short script works fine. And it is built-in by Apple. It simply writes to the .plist file (that's a type of file that stores the preferences you might change/edit. The contents of that file is what you see when you open any app's Preferences. However, there are often other things in it that you may not normally see. the "defaults write." method is the second safest way to make preference changes, the first is using the command-comma, normal method.
When you used the ShowAllFiles, did you insert the SDHC card? If you did you would have seen all those file names that your car's display is showing you. On removable volumes/drives, there will be a couple of "._" files and at least one "." file: .
_DS_Store, .
_Trashes and the infamous .DS_Store. There will also be several other folders/directories starting with ".": of course but also .fseventsd, .Spotlight-V100 (used by, surprise, Spotlight! assuming you haven't told Spotlight to ignore that volume) and .Trashes (guess what's in there!
).
The reason you see these files on the car's display is because it is
not using the Mac OS file system. It simply displays whatever it 'sees' on the card. I don't have such a modern system on my car, I have to burn a CD for this kind of thing. But that is done by creating a Playlist in iTunes (as
Paddy explains) and then burning the CD. When that method is used, the CD is recognized as an
audio CD and the car's system 'knows' what needs to be displayed. I assume that the same method will work on the SDHC drive. Sounds like
Paddy may have a 'smarter' car! I
know she has a
smarter brain! ;-)
When you simply drag and drop songs/files to the card (or even a CD) you are actually just moving the 'data' to that drive/card. Your car's system seems 'smart' enough to still be able to play the music files.
BTW, when you 'burn' the Playlist to the SDHC, notice that iTunes has a "Include CD text" (or similar text) on the first dialog you will see. If your car is as new ('smart') as I think it is, it will also write some other info on the card that may include the artist, genre, etc. My car is so old it can't even display the name of the
song!!