There are many standard UNIX directories that are invisible to Mac OS X’s Finder. Apple assumes that your normal OS X user does not want to see them. There are three ways a file will be invisible to the Finder:

  1. Files listed in /.hidden are hidden.
  2. Files that begin with a dot are hidden.
  3. Files that have their invisible attribute set are hidden.

We can make all hidden files visible to the Finder, as well as show selected hidden files.

You can show all hidden files in the Finder, by doing

defaults write AppleShowAllFiles YES

in a Terminal window. I don’t do this because it’s just too much information (replace YES with NO above to undo). For files that just have their invisible attribute set, try:

sudo /Developer/Tools/SetFile -a v /usr

You have to relaunch the Finder for this to take effect (Option-CMD-ESC, select Finder, and hit the “Relaunch” button). This way I can turn on just the files/directories that I want to see regularly. Note: you can use Go > Go to Folder from Finder’s menu to go to any directory, even hidden ones. This is handy for directories I don’t visit regularly, but do want to browse occasionally.

Here’s a reference to some of the hidden files.