With the simple look of the command-line interface, organizations don't always realize the advantages it brings to systems through pointed, accurate commands.
The main advantage of a command-line interface is that it provides a simple, accurate, keyboard-based method for interacting with all types of computer programs.
Graphical user interfaces, such as early versions of Microsoft Windows, quickly pushed command-line interfaces (CLIs) into disuse, yet even the most attractive GUIs could not completely diminish it. Despite its lack of visual appeal, the CLI provides precise control and sophisticated scripting suited to enterprise-class IT infrastructures.
Even now, CLIs remain a key part of any administrator's tool set.
Precise and broad control
Command-line interfaces rely on an extensive series of commands and services, which are sub-tools that admins can call through the CLI. These commands and services employ command-line switches and parameters, which provide granular control over the behavior of the command and the scope of the systems affected.
A CLI command can deploy a specific behavior on one server or system. But the desired command can also implement a behavior or effect on a group of systems -- or even all the systems -- that use the same command-line with the proper switches and parameters.
Using detailed commands through a command-line interface can be faster and more efficient than scrolling across GUI tabs and dialogs. This can be particularly powerful when handling highly repetitive tasks across many systems, and it demonstrates the advantages of a command-line interface.
Suppose an administrator has to move 1,000 files. Clicking through a GUI to move each file would be time-consuming and error-prone. But using a properly structured command through a command-line interface can vastly accelerate the process, as well as reduce overlooked items and errors.
Consider the granular control offered by command lines. For example, the Set-Location cmdlet in PowerShell sets or points the system to a desired location, such as a directory, sub-directory, registry location or other path. It uses the following detailed syntax:
Set-Location
[[-Path] <String>]
[-PassThru]
[-UseTransaction]
[<CommonParameters>]
An actual Set-Location command line might appear as:
PS C:\> Set-Location -Path "AppData:"
PS AppData:\>
As a more complex example, the PowerShell Get-WinEvent cmdlet enables administrators to retrieve events, logs and trace files from local or remote computers to assist with troubleshooting and configuration tasks. The Get-WinEvent cmdlet uses the following syntax:
Get-WinEvent
[[-LogName] <String[]>]
[-MaxEvents <Int64>]
[-ComputerName <String>]
[-Credential <PSCredential>]
[-FilterXPath <String>]
[-Force]
[-Oldest]
[<CommonParameters>]
The cmdlet uses an array of arguments that enable administrators to detail the desired log name specific computer and apply filters.
An actual Get-WinEvent command line can retrieve all of the event logs from a server named ServerOne with:
Many CLIs support the use of an alias, which replaces complex, frequently used command strings with simpler, shorter representations. Some CLIs even allow an alias to include default arguments to further simplify the command line.
PowerShell command lines provide administrators with a simplified way to easily execute tasks.
Interfaces such as Windows PowerShell provide a series of default alias commands. For example, an alias of either cd or chdir can replace the PowerShell Set-Location cmdlet.
PowerShell employs the New-Alias cmdlet to create new aliases. To replace the copy-item cmdlet with an alias, such as cit, an administrator could use the New-Alias cmdlet as follows:
PS C:\> new-alias cit copy-item
Now, the administrator can type cit to copy a specified item rather than typing the entire copy-item cmdlet. It's important to note that although some CLIs allow a new alias to include default parameters, the PowerShell CLI does not allow an alias to include arguments. Instead, admins must add new arguments to PowerShell's preferences, such as the $PSDefaultParameterValues file.
Still, administrators can see the advantages of a command-line interface with complex command string aliases.
Basic automation
Admins enter commands and arguments as text, and the CLI reads them and parses them as such.
Consequently, it is simple to save complex commands into a text file, apply a meaningful or descriptive name to that saved text file, and execute those saved text files as-needed. The capability to record or save CLI command strings reduces the need to retype complex command lines, and it can help admins deploy a series of detailed commands for complex, repetitive tasks.
Some older CLIs relied on simple, unformatted text files, but the advantages of a newer command line interface are that it might employ other formats. For example, PowerShell records command lines in an executable PS1 format. But it is also possible to script multiple command lines in the same text file.
This enables administrators to script a lengthy series of detailed commands that they can invoke as desired to perform complex, repetitive tasks. For example, admins can use a script to configure a new employee's credentials in Active Directory, check the configuration of any system on the network or provision storage for an application or VM.
Although there are many flexible, user-friendly automation platforms available to administrators, CLI scripts remain a commonly used -- and free -- way to document and handle almost any IT task.
Scripts meet the general goals of automation through accelerated, consistent task execution. They also reduce human error, such as typos and forgotten or incorrect arguments.
Additional advantages of a command-line interface
CLIs are desirable because they are simple, stable tools. As a result, they are rarely updated.
A CLI such as PowerShell may receive an update to support new cmdlets, but the underlying engine almost never changes. PowerShell first appeared in November 2006, but its 6.0 release only appeared in January 2018.
CLIs also demand little system overhead, and they lack audiovisual frills or graphical blandishments that require excess resources or network bandwidth.
The CLI's stability and reliability are genuine benefits in any IT environment where administrators deal with frequent application patches and updates.
CLIs also demand little system overhead, and they lack audiovisual frills or graphical blandishments that require excess resources or network bandwidth. This means CLIs can operate on the simplest, low-resolution monitors and mobile devices for convenient remote system management.
Don't ignore the downsides
There are multiple advantages to a command-line interface, but they also have a large drawback: a steep learning curve. Each CLI can impose extensive language and syntax -- all of which administrators must memorize.
Command lines are extremely sensitive to spaces and punctuation, which can lead to confusion and errors that affect a multitude of systems.
To avoid this, administrators should test critical command lines and scripts before deployment in a production environment.
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