Hidden file and hidden directory

In computing, a hidden folder (sometimes hidden directory) or hidden file is a folder or file which filesystem utilities do not display by default when showing a directory listing. They are commonly used for storing user preferences or preserving the state of a utility, and are frequently created implicitly by using various utilities. They are not a security mechanism because access is not restricted - usually the intent is simply not "clutter" the display of the contents of a directory listing with files the user did not directly create.

In Unix-like operating systems, any file or folder that starts with a dot character (for example, /home/user/.config), commonly called a dot file or dotfile, is to be treated as hidden – that is, the ls command does not display them unless the -a flag (ls -a) is used. In most command-line shells, wildcards will not match files whose names start with . unless the wildcard itself starts with an explicit . (although this is sometimes configurable; for example, the dotglob option in bash).

The notion that filenames preceded by a . should be hidden in Unix was probably an unintended consequence of trying to make ls not show . and ...

A convention arose of using dotfile in the user's home directory to store per-user configuration or informational text. Early uses of this were the well-known dotfiles .profile, .login, and .cshrc, which are configuration files for the Bourne shell and C shell and shells compatible with them, and .plan and .project, both used by the finger and name commands. Many applications, from bash to desktop environments such as GNOME now store their per-user configuration this way, but the Unix/Linux freedesktop.org XDG Base Directory Specification aims to migrate user config files from dotfiles in $HOME to non-hidden files in $HOME/.config - a hidden directory.

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