Command-Line Interface (CLI)

A command-line interface (CLI) is a means of interaction with a computer program where the user (or client) issues commands to the program in the form of successive lines of text (command lines).The CLI was the primary means of human interaction with most early operating systems, including MS-DOS, CP/M, Unix, and Apple DOS. The interface is usually implemented with a command line shell, which is a program that accepts commands as text input and converts commands to appropriate operating system functions.

Ease 

Because of the memorization and familiarity needed to operate a command line interface, new users have a difficult time navigating and operating a command line interface.

Control

Users have much more control of their file system and operating system in a command line interface. For example, users can copy a specific file from one location to another with a one-line command.

Multitasking

Although many command line environments are capable of multitasking, they do not offer the same ease and ability to view multiple things at once on one screen.

Speed

Command line users only need to use their keyboards to navigate a command line interface and often only need to execute a few lines to perform a task.

Resources

A computer that is only using the command line takes a lot less of the computers system resources than a GUI.

Scripting

A command line interface enables a user to script a sequence of commands to perform a task or execute a program.

Remote access

When accessing another computer or networking device over a network, a user will only be able to manipulate the device or its files using a command line interface.

Advantages of CLI:

= Most folks that have computer technology as a career are familiar with using this interface, especially if they have a *nix background.
= Requires a lower threshold for the interface. This means that a relatively simple program like telnet (available almost on all machines) is all you need to interface via CLI.
= Easy to integrate with scripting, and other programmatic interfaces.
= They can be quite powerful in the right hands. Piping multiple commands together, parsing feedback, etc.
= Many of the most common CLI executables in the *nix world are consistently ported, so there is a lot of consistency across systems.

Disadvantages of CLI:

= Not intuitive, especially to a lay user.
= No media.
= Complex combinations can be difficult to remember, and slower to type (but that is on a task by task basis, as often you can perform tasks faster with CLI)