If you've been around this site for a while, you know that the "defaults" command in Terminal can do a lot. It can set many hidden settings and preferences in Mac OS X, and in individual applications.

Mathias Bynens has posted a long list of these commands on github. I haven't looked closely, but I'm willing to bet that some of them haven't been posted here as hints yet.

There used to be a great tool called Secrets, which was a preference pane, and which allowed GUI access to many of these commands. Alas, Secrets hasn't been updated for Lion, so using Terminal is the best way to apply these commands.

If you're unfamiliar with how to use these commands, here's what you need to know. Open Terminal (in /Applications/Utilities), then paste one of the commands into Terminal and press Return. The commands in the list are the parts that begin with "defaults," such as:

defaults write com.apple.dock no-glass -bool true

This command removes the 3D graphics from the Dock.

Thanks to appstorm Mac for pointing out this page.

In 10.7, Apple changed Terminal to include a drop-down path icon in the window's title bar, similar to what you get in Finder and many other applications.

While some may like this, the problem is that it actually changes the window's title, as seen by applications (such as our own window manager, Moom). For instance, run this command in 10.7's Terminal...

osascript -e "tell application \"Terminal"\ to return name of window 1"

...and you'll see the current folder reflected in the window title. If you'd rather not have the path there, the fix is simple. Just add this command to your .profile file (or whatever file you use to init your Terminal windows):

unset PROMPT_COMMAND

Save the .profile file, close and open a new Terminal window, and you'll see that the folder drop-down has vanished from the window title.

In iTunes, there are two ways to categorize your videos: as either Movies or TV Shows. I use the Movies category for very large files, and put everything else in TV Shows, because in the TV Shows library, iTunes allows you to create groups. I've created groups called You Tube Videos, Home Videos, Work Stuff, etc.

To create a group, first make sure both TV Shows and Movies are visible in the iTunes source list. If they're not, go to iTunes' General preferences and check Movies and TV Shows in the Show section.

Next, import your new movie into iTunes by dragging it to the source list where these libraries display. In most cases, iTunes will categorize it as a movie. Select the movie and press Command-I to display the Info window. Click on the Options tab, then, under Media Kind, choose TV Show. If it's as short video, you might want to uncheck Remember Playback Position, because you will most likely always want to start these types of files from the beginning.

Next, click on the Sorting tab. Correct the tag that iTunes applied, if necessary, in the Name field. To create a nested group, you must enter some text in the Show field. You'll want to apply the same name for every item in the group, so the files stay in that group. Click on OK, and this will be applied.

When you look at your TV Shows library now, you'll see that all members of a group will display, in Icon or Cover Flow view, behind a single icon. In Album List view, all of the videos will display, but you'll see them sorted by "Show," or the group name you gave them.

[kirkmc adds: This is a good workraound that can help you organize a big video library, though there are some problems. iTunes seems to choose arbitrarily which icon to display when in icon view, rather than, say, the first item.

Another way you could do this, if you want to display the items in Icon view, is to choose to display them by Genre, and apply custom genres to your video files. However, using the Show tag allows this organization to also display on an Apple TV.]

My workflow often involves taking Word Documents and manipulating them with handwritten annotations on my iPad. With this method, I can immediately take a downloaded .docx (or presumably any other MS Office file), convert it to a PDF, get it into my Dropbox, and finally my annotation app; all without leaving the iPad. While it may seem clumsy at first, it only takes four easy steps.

You will need the Pages app, the Dropbox app, a Dropbox account, and a a send to dropbox account.
1. Import your document into the Pages app.
2. Tap the wrench and select "Share and print."
3. Email a PDF to your @sendtodropbox address.
4. Check out the "Attachments" folder in Dropbox (or your desired Dropbox-linked 3rd party app).

[kirkmc adds: I haven't tested this.]

I'd come across this before, and it was very annoying. Last night, I downloaded a zip archive of freely-distributed MP3 files, and when I double-clicked it to decompress it, all I got was a .cpgz file. This is apparently a zipped CPIO archive file. Double-clicking that file just created the zip file again, and this was an endless loop

Searching on Google, I saw that plenty of people had come across this problem, and offered a number of suggestions, none of which worked for me. Some articles suggested that the download might have been corrupted, but as this was a very large file, I didn't want to try and download it again.

The solution for me was to use the free The Unarchiver, which has turned out to be a Swiss army knife for decompressing many obscure types of archives. Opening the file with The Unarchiver decompressed it correctly.

I didn't think of it at the time - and I have since deleted the archive - but the cpio command would probably have worked via Terminal as well. In any case, if you encounter this odd archive decompression loop, here's an easy way to solve the problem

The other day on Twitter, Macworld senior editor Dan Frakes mentioned that he had accidentally discovered an undocumented keyboard shortcut to delete messages in Mail. My guess is that he just leaned on his keyboard, but he figured out, after deleting a number of messages, that this shortcut is Control-H.

This makes sense, as this is the Unix keybinding for the Backspace or Delete key (see this Wikipedia article), and OS X uses these shortcuts, at least in Cocoa applications; you can use the Control-H shortcut to delete text in those applications that use the Cocoa text input framework. But its use to delete messages in Mail is interesting. If anyone discovers other apps where this works, post them in the comments.

The latest update to Google Earth for iOS, version 6.2, can open .kmz or .kml files on websites, but you can also e-mail these to yourself to use on your iPhone or iPad. If you're in the desktop version of Google Earth, right-click on a link and choose Email..., and a new message will be made with the .kmz file as an attachment. When you receive this on your iOS device, tap and hold, then open the file with Google Earth.

[kirkmc adds: This works as described. I have to say, the only time I ever open Google Earth is to follow the route of the Tour de France...]

Apparently, there are cases when exporting a song from GarageBand to iTunes results in a time-out. Apple has published a technical note explaining that this may occur if there are any open dialogs in iTunes. Make sure to close all such windows in iTunes - such as the Preferences or Info windows - before exporting songs from GarageBand.

iTunes 10.6, just out, has a new feature that some music lovers will appreciate. In the past, you could auto-convert music files when syncing them to an iPod or iOS device, but only to 128 kbps. Now, with iTunes 10.6, you have three options: 128, 192 and 256 kbps. This is available in the Options section of the Summary tab for an iPod.

[kirkmc adds: While not strictly a hint, but rather a heads up for a new feature, this is a one that many iTunes users have been hoping for. I blogged about it, but thought it would be useful to have it here as well.]

Apple recently announced that iTunes in the Cloud was extended to include movies purchased from the iTunes Store. A post on the Tech of the Hub website points out that not only can you re-download or stream iTunes Store purchases, but that some "digital copies" of movies, which you get on some Blu-Ray discs, are also recognized.

So if you have any Blu-Rays with these digital copies, and you haven't bothered to put them in your iTunes library, you might want to do so. If they are matched, you can access them from other devices more easily.

Note: as the blog post points out, not all the movie studios are on board with this yet. So you will certainly find movies that don't match from digital copies.