Chapter 14. Preferences and Defaults

Whenever you customize the behavior of a Mac OS X application, such as changing the default font or colors or the windows that are visible, the various changes you make are saved into a preference file for that application. This is in contrast with Windows where application preferences typically are saved into the monolithic registry. And because each application stores its preferences in a separate file, the overall system is more robust than if all the preferences were in one big file. If a preference gets corrupted, it is less likely to affect the system and typically affects only the application that uses that preference. The designated location for preference data is the Library/Preferences folder in each of the filesystem domains. (Review Chapter 3 for more information about filesystem domains.)

Many Mac OS X applications, including all the applications Apple provides, go beyond just using the Library/Preferences directory and store their preferences in the defaults system . This system, which is often referred to as the defaults database, is made of each application's preferences stored in an XML-based property list (plist) file in the Preferences folder. By using the defaults system, applications can use code in the operating system to manage preferences instead of having to provide their own preference-handling code. Additionally, you can use the defaults command in the Terminal to read and write data into the defaults database.