How to open iCloud CDT file

I found this site which details iCloud a bit more, on it, it talks about .CDT files and how they can be 'unzipped' and read as a .plist. As I am having issues with iCloud I thought I could at least see what was in them and see what exactly is being uploaded.

However, when right-clicking on the .CDT files there is no option to unzip them, nor do they open in Xcode.

Thanks for any replies!

Solution

They're zip files all right, but the cdt extension makes Mac OS X think they're something else. You can either

Copy them somewhere and change the "cdt" extension to "zip", or
Unzip them at the command line, using "unzip".

They contain a binary property list file named "contents".