Microsoft PowerShell

What is PowerShell?

PowerShell is a cross-platform task automation and configuration management framework, consisting of a command-line shell and scripting language. Unlike most shells, which accept and return text, PowerShell is built on top of the .NET Common Language Runtime (CLR), and accepts and returns .NET objects. This fundamental change brings entirely new tools and methods for automation.

Output is object-based

Unlike traditional command-line interfaces, PowerShell cmdlets are designed to deal with objects. An object is structured information that is more than just the string of characters appearing on the screen. Command output always carries extra information that you can use if you need it.

If you’ve used text-processing tools to process data in the past, you’ll find that they behave differently when used in PowerShell. In most cases, you don’t need text-processing tools to extract specific information. You directly access portions of the data using standard PowerShell object syntax.

The command family is extensible

Interfaces such as cmd.exe don’t provide a way for you to directly extend the built-in command set. You can create external command-line tools that run in cmd.exe. But these external tools don’t have services, such as Help integration. cmd.exe doesn’t automatically know that these external tools are valid commands.

The commands in PowerShell are known as cmdlets. You can use each cmdlet separately, but their power is realized when you combine them to perform complex tasks. Like many shells, PowerShell gives you access to the file system on the computer. PowerShell providers enable you to access other data stores, such as the registry and the certificate stores, as easily as you access the file system.

You can create your own cmdlet and function modules using compiled code or scripts. Modules can add cmdlets and providers to the shell. PowerShell also supports scripts that are analogous to UNIX shell scripts and cmd.exe batch files.

Support for command aliases

PowerShell supports aliases to refer to commands by alternate names. Aliasing allows users with experience in other shells to use common command names that they already know for similar operations in PowerShell.

Aliasing associates a new name with another command. For example, PowerShell has an internal function named Clear-Host that clears the output window. You can type either the cls or clear alias at a command prompt. PowerShell interprets these aliases and runs the Clear-Host function.

This feature helps users to learn PowerShell. First, most cmd.exe and Unix users have a large repertoire of commands that users already know by name. The PowerShell equivalents may not produce identical results. However, the results are close enough that users can do work without knowing the PowerShell command name. “Muscle memory” is another major source of frustration when learning a new command shell. If you have used cmd.exe for years, you might reflexively type the cls command to clear the screen. Without the alias for Clear-Host, you receive an error message and won’t know what to do to clear the output.

PowerShell handles console input and display

When you type a command, PowerShell always processes the command-line input directly. PowerShell also formats the output that you see on the screen. This difference is significant because it reduces the work required of each cmdlet. It ensures that you can always do things the same way with any cmdlet. Cmdlet developers don’t need to write code to parse the command-line arguments or format the output.

Traditional command-line tools have their own schemes for requesting and displaying Help. Some command-line tools use /? to trigger the Help display; others use -?/H, or even //. Some will display Help in a GUI window, rather than in the console display. If you use the wrong parameter, the tool might ignore what you typed and begin executing a task automatically. Since PowerShell automatically parses and processes the command line, the -? parameter always means “show me Help for this command”.


PowerShell has a pipeline

Pipelines are arguably the most valuable concept used in command-line interfaces. When used properly, pipelines reduce the effort of using complex commands and make it easier to see the flow of work. Each command in a pipeline passes its output, item by item, to the next command. Commands don’t have to handle more than one item at a time. The result is reduced resource consumption and the ability to get output immediately.

The notation used for pipelines is similar to the notation used in other shells. At first glance, it may not be apparent how pipelines are different in PowerShell. Although you see text on the screen, PowerShell pipes objects, not text, between commands.

For example, if you use the Out-Host cmdlet to force a page-by-page display of output from another command, the output looks just like the normal text displayed on the screen, broken up into pages:

Get-ChildItem | Out-Host -Paging
    Directory: /mnt/c/Git/PS-Docs/PowerShell-Docs/reference/7.0/Microsoft.PowerShell.Core

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d----          05/22/2020    08:30                About
-----          05/20/2020    14:36           9044
-----          05/20/2020    14:36          12227
-----          05/20/2020    14:36           3566
-----          05/20/2020    14:36          29087
-----          05/20/2020    14:36           5705
-----          05/20/2020    14:36           3515
-----          05/20/2020    14:36          25531
-----          05/20/2020    14:36           7852
-----          05/20/2020    14:36          25355
-----          05/20/2020    14:36           3491
-----          05/20/2020    14:36          13310
-----          05/20/2020    14:36           8401
-----          05/20/2020    14:36           9531
<SPACE> next page; <CR> next line; Q quit

Paging also reduces CPU utilization because processing transfers to the Out-Host cmdlet when it has a complete page ready to display. The cmdlets that precede it in the pipeline pause execution until the next page of output is available.

Objects in the pipeline

When you run a cmdlet in PowerShell, you see text output because it is necessary to represent objects as text in a console window. The text output may not display all of the properties of the object being output.

For example, consider the Get-Location cmdlet. The text output is a summary of information, not a complete representation of the object returned by Get-Location. The heading in the output is added by the process that formats the data for onscreen display.


Piping the output to the Get-Member cmdlet displays information about the object returned by Get-Location.

Get-Location | Get-Member
   TypeName: System.Management.Automation.PathInfo

Name         MemberType Definition
----         ---------- ----------
Equals       Method     bool Equals(System.Object obj)
GetHashCode  Method     int GetHashCode()
GetType      Method     type GetType()
ToString     Method     string ToString()
Drive        Property   System.Management.Automation.PSDriveInfo Drive {get;}
Path         Property   string Path {get;}
Provider     Property   System.Management.Automation.ProviderInfo Provider {get;}
ProviderPath Property   string ProviderPath {get;}

Get-Location returns a PathInfo object that contains the current path and other information.

Built-in help system

Similar to Unix man pages, PowerShell includes detailed help articles that explain PowerShell concepts and command syntax. Use the Get-Help cmdlet to display these articles at the command prompt or view the most recently updated versions of these articles in the PowerShell documentation online.