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Invisible Files: What Files Are Invisible?

Numerous files on a Mac OS X volume are deliberately set to be invisible. In this section, I explore what these files are and why they are set to be invisible. I also explain why and how to access them.

Files that begin with a dot (.)

If the first character of a file name is a period/dot (.), Mac OS X interprets that to mean that the file should be invisible. Some invisible files of interest that begin with a period include:

.Trash. This directory contains items you place in the Trash and is located at the root level of your Home directory.

.DS_Store. This file, which is likely to pop up in virtually every folder you access, stores the data needed to remember the location of icons in icon view for that folder.

Unfortunately, its memory is not always good. I still have problems when icons rearrange themselves spontaneously, especially on the Desktop and after waking from sleep.

.FBC files (such as .FBCIndex). These files are used in the Find by Content (FBC) Sherlock index searches. The .FBCIndex file is located at the root level of your Home directory.

.hidden. This special file contains a list of files (whose names do not begin with a dot) that are to be kept invisible. I discuss this file in the following section.

Files in the .hidden list

The .hidden file is stored at the root level of the Mac OS X volume. The easiest way to open and view its contents is to use the freeware program BBEdit Lite for Mac OS X. Follow these steps:

  1. Launch BBEdit, and choose Open Hidden from the File menu.

  2. In the window that appears, slide the browser's scrollbar all the way to the left.

  3. Select the name of your Mac OS X startup volume in the leftmost column. The .hidden file should be listed in the column immediately to the right.

  4. Double-click .hidden to open it.

You will see that its list contains root-level items, including the Mac OS 9 Desktop database files (Desktop DB and Desktop DF), the Mac OS 9 Desktop folder, the mach files (the mach_kernel file in particular is critical to the running of Mac OS X), and Unix folders (such as etc and bin).

The rationale, as in virtually all cases of invisible files, is that keeping these files invisible minimizes the chance that users will meddle with them. Typical users will rarely, if ever, need to modify these files, but the files could cause trouble if they are moved or deleted.

Although you could modify this .hidden file (you would need root access to do so) and thus change the invisibility of the listed files, I generally recommend not doing so. You can modify invisibility in other ways, if necessary.

SEE

"Modifying Unix Files," later in this chapter, for one example of using BBEdit to modify an invisible file.

NOTE

Some of the files that are invisible in Mac OS X may be visible in Mac OS 9. Also, some files that are invisible on the Mac OS X startup volume may be visible on other volumes, even when you're booted in Mac OS X. The Desktop and Temporary Items folders, for example, are visible in all partitions other than the Mac OS X partition.

Figure 6.38Figure 6.38 BBEdit's Open Hidden command.


Files with the Invisible (Hidden) bit set

The Invisible bit is a leftover from Mac OS 9. Turning on this bit was the main way of making a file invisible in Mac OS 9, and it still works in Mac OS X. Some files may have the Invisible bit set and also have their names begin with a dot. Perhaps this setup makes them doubly invisible.

Accessing and modifying the Invisible bit requires special utilities, described in the following section.

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