Command prompt

The term has many synonyms, among them shell, command shell and command processor. A shell is a program through which the user (or administrator) controls the operating system and the installed programs, using the command line. The shell differs from most other programs in that it is only a means to perform certain tasks, not the task itself. Shell runs inside a terminal and invites you to enter commands.

Each line sent to the system by the user is a command that the system must execute. After typing the command, you must press Enter to execute it. Until then it can be edited.

The $ symbol is used as a separator. To the left of it is the configurable message to output, usually the current directory, and to the right is what the user enters. All examples in the following will be demonstrated without this message and symbol. Below is an example of using the date command, which outputs the current date.

The command shell allows you to run installed programs, but that is not all it can do. For comfortable work it is useful to have autocompletion of program and file names, history of entered commands, ability to navigate in the file system, convenient hotkeys, scripts support. Later in the course we will cover many of these aspects. Command shells, like terminals, are different, although most operating systems default to Bash.

A shell and a terminal are not the same thing. A terminal is a program that runs a shell inside itself.