Display Hidden Files In Finder

Hidden files in Mac OS X keep essential operating system data safe from casual tampering. The technique leaves the Finder uncluttered and easy to navigate, and diminishes the chance of accidental damage. But hidden files also the contain preferences for command line tools, serial numbers for commercial products, access controls for HTML directories, and the entire Unix subsystem that keeps your Macintoshes running. They're often useful for troubleshooting, and the ability to temporarily access them can be an invaluable tool for administrators.

Fortunately, there's a painless way to display these files when you're tracking down a problem on someone else's machine, and just as importantly a way to hide them again when you're done. Open the Terminal and type the following:

defaults write com.apple.finder AppleShowAllFiles -bool TRUE

Now hold down the option and command keys, and select the Finder icon in the dock. Choose "Relaunch" from the pop-up menu, and when your windows redraw they'll be full of your invisible files and folders, distinguished with lighter colored icons.

Keep in mind that working with hidden files can disable or even destroy your operating system. So when you're done, you'll want to put the system back the way you found it. To safely conceal your previously-hidden files, just run the above command again, replacing TRUE with FALSE and relaunching the Finder afterwards.

With this technique, you can harness the power of the command line while retaining the convenience of the graphical interface.

Recommended Reading: Ted Landau has a great article on the various kinds of "Invisible Files in Mac OS X" at MacFixit. Even more exhaustive is Gordon Davisson's wonderful chart of "Mac OS X Hidden Files & Directories", from Seattle's Westwind Computing.