File system

Special filenames

Some filenames have special meaning:

name meaning
. The current directory.
.. The parent directory of any given directory.
/ The root directory.
(It’s \ on Windows).
By no coincidence, this is also the path separator.

Unix only

name meaning
.config
.secrets		 Filenames beginning with . are hidden files and will not normally be displayed when you ask for a directory listing.
~ Your home directory.
This is the current directory when you first log in. If you make or download any files, this is where you usually save them.
~olivia User olivia’s home directory (you won’t necessarily have permission to look inside it).

Most Unix systems have conventions for the name of system directories too. A few of them are described below. It’s a good idea to become familiar with these so you can find your way about. Remember these are only conventions, so individual systems might do things a little differently:

name use
/bin Binary files — files that contain the instructions the machine follows for implementing commands or fundamental utilities.
/dev Devices — file representations of things like printers and terminals.
/home The directory containing each user’s home directory. For example, Olivia’s home directory would be /home/olivia (which is the absolute file path of ~olivia, above).
/sbin System binaries, like /bin but with executables critical for system operation.
/tmp Temporary files.
/usr 1 Executables, libraries, and shared resources that are not part of the core system.
/var “Variable” files — files expected to change a lot.
/var/log System log files.
/var/tmp Temporary files.

Note that these are all conveniently expressed as absolute file paths: they are found in the root directory.

1 Originally, /usr was an abbreviation for "user" because it contained the users' files, but in today's Unix systems that's what the /home directory is for. So it's more helpful to remember /usr as an abbreviation of "user system resources". If you install a new application, it probably ends up here.