Mac OS X Tiger in a Nutshell

Dotfiles

Following the traditional Unix model, the Finder hides all dotfiles , which are simply files (or folders) whose names begin with a period (dot) character. Applications can access dotfiles like any other file.

Your Mac’s filesystem will likely accrue many dotfiles over time, particularly in users’ Home folders, since this is the typical location for legacy Unix applications to store preference and configuration files. (Mac OS X-specific applications prefer to store this sort of information in Library folders, as described in the earlier section "The Library folder“.) The following list covers some of particular interest:

.bash_history

Found in the user’s Home directory, this file is used by the bash shell to record previously entered commands.

.FBCIndex, .FBCLockFolder

The Finder creates these dotfiles in each directory that it indexes by content. The binary file, FBCIndex, acts as an index to the content of all the folder’s files. When performing a by-content search via the Finder’s Find command, the Finder quickly reads from these index files, rather than picking through all the individual files again.

.ssh

When you access another computer via the Secure Shell (SSH), an encrypted RSA key is stored in the known_hosts file within this directory.

.Trash

Found in users’ Home folders, this directory contains all the files and folders that a user has sent to the Trash (through either the Dock’s Trash icon or the Finder’s Move to Trash (-Delete) command) but not yet deleted. ...