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File System Organization

The Mac OS X file system organization is slightly different from that of most UNIX environments, and is described in detail in the man page hier. This section presents only the most important differences between a typical UNIX environment and Mac OS X.

First, Mac OS X has a number of folders intended primarily for use with GUI applications or for parts of Mac OS X itself. These paths generally start with a capital letter, and include:

• /Applications—contains GUI applications

• /System—contains system frameworks and parts of the OS itself

• /Library—contains primarily user-installed frameworks

• /Developer—contains the developer tools (if installed)

• /Users—contains the home directories of local users

In addition, various ports collections are available, and install files in various locations, such as /sw (fink), /usr/local (GNU-Darwin), and /opt/local/ (Darwin Ports).

A few directories, including /etc and /tmp are actually symbolic links into /private. You should be careful not to stomp on these symbolic links.

Finally, you should be aware that by default, a number of directories are hidden from users when viewing the file system using the Mac OS X GUI. These directories include most of the standard system directories, including /bin, /dev, /etc, /sbin, /tmp, and /usr. These directories still appear and behave in the expected manner when accessed from the command line. For more information on making these visible from GUI applications, see “File-System Structure and Visibility.”

Mac OS X has different privilege sets for file system access. Users by default have write access to their home directory and certain other directories created in previous versions of Mac OS. Admin users have write access to additional parts of the system, including various application directories and configuration files, without the need to become the root user. Finally, the directories containing the OS itself are read-only except as root.

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