What Is a CLI? Command Line Interface Commands and Functions

The command line interface tool has existed since the early days of computing. It allows users to interact with their systems with just a few keystrokes and text-based commands. In this article, learn what a command line interface (CLI) is, how it works, and what commands you should use to optimize your computer.

What is a command line interface?

A command-line interface (CLI), also known as a command-line user interface, is a text-based user interface (TUI) for interacting with a computer. The CLI lets you communicate directly with your computer's operating system or software application to execute numerous operations.

CLIs require users to input lines of text called commands. A command is a thing that tells your system what you want it to do. Usually, you enter these textual commands into a command prompt or terminal using a keyboard. Your computer then responds to these commands by running them.

This means CLI is a means of interacting with a computer in a more text-based manner. Beyond that, you can use the CLI tool to navigate, run programs, and configure computer programs quickly.

Today, major operating systems, including Windows, Linux, and macOS, offer a graphical user interface (GUI) as a default. Most users rely on it more than command-line interfaces. Most current Unix-based systems, on the other hand, provide a command line interface alongside the graphical user interface. The CLI is for faster system interaction.

However, the availability of the CLI varies between operating systems. In Microsoft Windows, you can use PowerShell and command prompt (cmd) as command line interfaces. macOS also as a CLI called Terminal, which can be accessed through a shortcut or by typing "Terminal" into the Spotlight search. Even programming languages, such as Python, support command-line interfaces.

CLIs are made possible by command-line processors or command-line interpreters. These are the programs that not only read command lines but carry out the commands as well.

The increasing use of CLIs to automate repetitive tasks is evidence that this tool is valuable for many users. System administrators, software developers, IT experts, and network admins prefer a reproducible interface for managing their systems.

How does a command line interface work?

Command line interfaces were used extensively in the early days of computing, as they were the only way to interact with computers before graphical user interfaces were developed. With CLI, you can run programs, create and delete files, and navigate through folders.

A CLI runs with the help of commands. In a CLI, you enter commands as text, and the computer's operating system then executes these commands. The computer can be anything from launching a program to managing files to configuring the operating system.

The system is responsible for interpreting the command as well as carrying out the corresponding operation. The CLI provides feedback in the form of text-based responses, such as status messages.

Keep in mind that a CLI operates based on a set of predefined commands, which can vary depending on the operating system being used. The three types of CLI commands that can be entered include:

• System commands. The commands are encoded as part of the operating system and are available to use without installing additional software. They are essential for managing the underlying operating system.
• Executable programs. They run text-based or graphical applications. Executable programs help you perform more complex tasks than system commands like connecting to network devices.
• Batch programs or scripts. Scripts are text files that contain a list of commands to be executed sequentially. These can perform multiple tasks in succession, making it easier to automate repetitive processes.

These commands offer users a range of capabilities in interacting with a computer via the CLI. They contain a distinct syntax and must exist written in the same line to avoid error messages.

Common CLI commands

A command line relies on commands to perform tasks. It's also important to point out that a command line is a mixture of prompts and commands. Depending on the operating system, there are thousands of executable commands you can use to get the most out of your computer. These are the most useful MS-DOS commands.

Command	Example	Function
CD	CD C:\MyFolder	Changes the current directory to the specific directory
DIR	C:\> DIR	Lists the contents of the current directory
MKDIR	C:\ MKDIR c:\NewDIR	Creates a new directory with the specified name
MD	MD C:\NewFolder	Creates a new directory
COPY	COPY C:\File1.txt c:\File2.txt	Copies a file or directory
CHKDSK	CHKDSK C:	Checks the specified drive for errors and repairs them if necessary
FORMAT	FORMAT C:	Formats a disk and makes it ready for use
ATTRIB	ATTRIB +R C:\File5.txt	Sets or changes the attributes of a file
RMDIR	C:\> RMDIR c:\Backup	Removes a directory
MORE	C:\> MORE autoexec.bat	Displays contents of a file, one screen at a time
DEL	DEL C:\File3.txt	Deletes a file
REN	REN C:\OldName.txt C:\NewName.txt	Renames a file

These are just a few of the many MS-DOS commands available. Though some commands for CLI in MS-DOS now lack support, most still work in PowerShell as originally expected.

The majority of these commands are helpful for beginners. They provide the foundation for working with the CLI and are important to master for efficient command line usage.

Features of a command line interface

A command line interface isn't just a simple command; most of them come with a set of advanced features. Some additional command line interface features include:

• System variables, which are defined by the operating system. CLIs can use these features to access information about the system.
• Scripting capability, which enables users to write scripts. These automate tasks, perform complex operations, and make CLIs more user-friendly.
• Command pipes allow users to connect the output of one command to the input of another command. This can be used to perform complex operations that would otherwise feel impossible.
• Command history is a list of commands that the user has entered into the CLI. Users use this feature to quickly repeat previous commands, find a specific command that has been entered before, and learn about the commands used in the past.

The features make CLI stay relevant. Nowadays, many people are using CLIs to manage their cloud computing resources and automate their workflows.

Examples of CLIs in different operating systems

Most vendors set the CLI as the default command-line interface for their latest operating systems. Here are the most popular operating systems and their respective command-line interfaces.

• Windows. Command Prompt and PowerShell are command-line interfaces for Windows users. A user can access them by typing cmd or PowerShell into the search box. The command prompt is not as prominently featured in the GUI, but it's essential for users who need it.
• Linux. Linux operating systems come with a variety of CLI options, including Bash, Zsh, and Tcsh. The CLI is often the default interface for Linux systems, and it's heavily used by system administrators.
• macOS. macOS has a CLI called Terminal, which users can access by typing Terminal into the Spotlight search.
• Amazon Web Services. Another example of a command line interface is the AWS Command Line Interface. It is a unified tool provided by Amazon Web Services (AWS) to manage various AWS abilities.
• Google Cloud Platform. GCP uses the G-cloud command-line interface (CLI) to manage and interact with its services. It provides a wide range of commands for managing GCP resources, such as Compute Engine instances, Cloud Storage buckets, and Cloud Functions.
• Microsoft Azure. Azure users make use of Azure CLI bash as the command-line interface. The tool allows you to gain insights into Azure usage.

History of CLI

The command line interface emerged in the 1960s as the primary means of interacting with computer systems through text-based terminals. Users had to type a command on the CLI to perform tasks on the computer.

At that time, computer systems only had keyboards for input. The computer screens could only display text as output. The MS-DOS is one of the many examples that used the CLI as the standard user interface.

Going forward, command lines were also simple and limited in functionality. Users had to memorize specific commands and their syntax to perform tasks.

As computer systems grew in power, CLI interfaces developed more advanced features. The CLI has adapted to the changing needs of users over the years. Once Douglas Engelbart invented the mouse in the 1990s, it largely marked the end of point-and-click interaction, as many computer users opted for graphical user interfaces. Though GUIs have become popular, command lines are still favored and available in all operating systems today.

Benefits of a command line interface

Command line interfaces offer several benefits, including:

• Power. CLI commands allow you to do tasks that are impossible with GUIs. For example, you can use the command line to automate tasks, write scripts, and manage system resources.
• Control. CLIs give you more control over your computer. With it, you can directly manipulate files, system settings, and other aspects of your computer.
• Automation and scripting. The tool is crucial for automating repetitive tasks. You can easily create a batch file to automate tasks at any given time.
• Cross-platform abilities. Many commands work across different operating systems, making them applicable in various computing environments.
• Resources. CLI doesn't require a lot of computing resources or memory to execute commands as compared to a graphical interface.
• Speed execution. Once you master the CLI commands, which seem intimidating at first, you'll be able to execute complex tasks much faster than usual.
• Information retrieval. Command history features help retrieve information about the system, such as network status.

Limitations of a command line interface

Despite the power that a CLI offers, users face a few challenges. Command line interfaces can have a steep learning curve, which means they're difficult to learn if you aren't familiar with them.

Additionally, these interfaces are more prone to errors than GUIs. You're likely to make mistakes if you aren't careful. Finally, CLIs don't provide visual feedback, which can make them difficult for some users.

Who uses command line interfaces?

CLI is essential for system administrators who want to manage systems efficiently. CLI is what they depend on to configure their systems. Software developers leverage CLIs to build, test, and deploy software.

Network engineers are another group of people that use CLIs to automate infrastructure while security professionals enter CLI prompts to investigate security incidents and respond to threats.

Most importantly, CLIs offer a powerful tool for data scientists who need to analyze data to build machine learning models.

Frequently asked questions

What's the difference between CLI vs GUI?

Many computer users interact with these two types of interfaces because nearly every operating system offers both CLI and GUI. GUI is the most popular user interface in modern computing. It uses Windows, icons, menus, and other graphical elements to perform different tasks.

GUI is more user-friendly and easy to learn for novices. However, it's less powerful than a CLI. The command line is more efficient for repetitive tasks, hence a preferred tool for complicated computing.

Can I use CLI even if I'm not a programmer?

Yes, you don't need programming skills to use the CLI. Simple commands are available to help you navigate your computer.

What is command line interface used for?

You can use a command-line interface for system administration tasks, like monitoring computer resources, managing remote systems over a network connection, automating repetitive tasks, and configuring system settings. CLIs also work for collecting system longs and setting up web servers. Ultimately, they provide granular control over files and directories, allowing users to create, delete, move, copy, rename, or manipulate files.