In computer sciences, an alias is a name which usually designates an already-named reference.

Aliases are names used to designate objects, items and settings which already possess a name. In *nix systems, they usually serve as :

  • Hostnames ; a machine possesses a unique hostname, which can be surrounded by aliases. On a Linux system, you can find your hostname by typing hostname, whereas the /etc/hosts file might contain other aliases for the IP representation of your machine on its network interfaces.

  • Users ; on *nix systems, each user has a given name, registered in the /etc/passwd file. However, for some other purposes such as email processing, it might be useful to create aliases for users. This can be done in the /etc/aliases file. (e.g. root is usually aliased as the postmaster).

  • Shell commands ; on *nix systems, it is possible to set an alias referencing a command/program (with possible options and arguments). The most common one is probably ll, which designates ls -l (long list). An alias can be created using the alias (man page) command, and destroyed thanks to the unalias bash utility (man page).

One could also consider UNIX links as an implementation of aliases for files (in the UNIX meaning). See ln for more information (man page).

Each application handles its aliases as it wishes to. Some don't even implement this possibility, and expect the administrator to use the real resources names. Please refer to the applications' documentation for more information on specific cases.

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