Mac OS X Tiger in a Nutshell

Viewing and Modifying File Permissions

The permissions system is another part of Mac OS X with two distinct interfaces: you can either use the traditional Unix command-line tools through the Terminal to view and change a file’s permissions, or you can use the Finder’s Get Info window for a graphical interface to the same task.

Figure 9-5 shows the Finder’s interface to the permission system, a section of the Finder’s Info window .

Figure 9-5. The Get Info window’s Ownership & Permissions view

The pop-up menus display the object’s current owner and group, as well as the owner, group, and other access permissions.

If you are the file’s owner, you can modify the three permission menus, setting them to Read & Write, Read Only, or No Access for that type of user. If you have administrative privileges, you can also modify the object’s owner and group.

What About the Execute Bit?

Unix veterans will note that the Finder offers no interface to any of a file’s “execute” bits, which determine whether someone is allowed to try launching a file as a program. Simply put, this type of distinction doesn’t exist in Mac OS X’s Aqua layer, in which the Finder recognizes only certain kinds of files or directories as launchable, including .app application bundles and .jar Java archive files.

Furthermore, directories created in the Finder—through File→New Folder (Shift--N)--always have their execute bits set, ...