Hide and Show Mac Files using Terminal

Viewing hidden files on a Mac is useful for accessing the hidden UNIX directories or for recovering Music from an iPod. Additionally, by prefixing the name of a folder with a '.', you can create a folder that is seemingly hidden from prying eyes.

To view hidden folders:

1. Open the Terminal (located in /Applications/Utilities/)
2. At the command prompt type

   defaults write com.apple.finder AppleShowAllFiles -bool true

3. Press return to execute the command.
4. For the changes to take effect, either log out then log back in again, or relaunch Finder (this can be done from the Force Quit Window or by typing 'killall Finder' in a Terminal window).

To hide the hidden files again:

1. Open the Terminal
2. At the command prompt type

   defaults write com.apple.finder AppleShowAllFiles -bool false

3. then press return to execute the command.
4. Log out then back in again, or relaunch Finder (explained above).

Reference : http://guides.macrumors.com/