PowerShell

PowerShell is a shell program developed by Microsoft for task automation and configuration management. As is typical for a shell, it provides a command-line interpreter for interactive use and a script interpreter for automation via a language defined for it. Originally only for Windows, known as Windows PowerShell, it was made open-source and cross-platform on August 18, 2016, with the introduction of PowerShell Core. The former is built on the .NET Framework; the latter on .NET (previously .NET Core).

PowerShell is bundled with current versions of Windows and can be installed on macOS and Linux. Since Windows 10 build 14971, PowerShell replaced Command Prompt as the default command shell exposed by File Explorer.

In PowerShell, administrative tasks are generally performed via cmdlets (pronounced command-lets), which are specialized .NET classes implementing a particular operation. These work by accessing data in different data stores, like the file system or Windows Registry, which are made available to PowerShell via providers. Third-party developers can add cmdlets and providers to PowerShell. Cmdlets may be used by scripts, which may in turn be packaged into modules. Cmdlets work in tandem with the .NET API.

PowerShell's support for .NET Remoting, WS-Management, CIM, and SSH enables administrators to perform administrative tasks on both local and remote Windows systems. PowerShell also provides a hosting API with which the PowerShell runtime can be embedded inside other applications. These applications can then use PowerShell functionality to implement certain operations, including those exposed via the graphical interface. This capability has been used by Microsoft Exchange Server 2007 to expose its management functionality as PowerShell cmdlets and providers and implement the graphical management tools as PowerShell hosts which invoke the necessary cmdlets. Other Microsoft applications including Microsoft SQL Server 2008 also expose their management interface via PowerShell cmdlets.

PowerShell includes its own extensive, console-based help (similar to man pages in Unix shells) accessible via the Get-Help cmdlet. Updated local help contents can be retrieved from the Internet via the Update-Help cmdlet. Alternatively, help from the web can be acquired on a case-by-case basis via the -online switch to Get-Help.

Shell programs, including PowerShell, trace lineage to shells in older operating systems such as MS-DOS and Xenix which exposed system functionality to the user almost exclusively via a command-line interface (CLI) – although MS-DOS 5 also came with a complementary graphical DOS Shell. The Windows 9x family came bundled with COMMAND.COM, the command-line environment of MS-DOS. The Windows NT and Windows CE families, however, came with the newer cmd.exe – a significant upgrade from COMMAND.COM. Both environments provide CLI for both internal and external commands and automation via batch files – a relatively primitive language for scripting.

To address limitations of these shells – including the inability to directly use a software component exposed via COM – Microsoft introduced the Windows Script Host in 1998 with Windows 98, and its command-line based host, cscript.exe. It integrates with the Active Script engine and allows scripts to be written in compatible languages, such as JScript and VBScript. These scripts can use COM components directly, but it has relatively inaccessible documentation and gained a reputation as a system vulnerability vector after several high-profile computer viruses exploited weaknesses in its security provisions.

Different versions of Windows provided various special-purpose command-line interpreters (such as netsh and WMIC) with their own command sets but they were not interoperable. Windows Server 2003 further attempted to improve the command-line experience but scripting support was still unsatisfactory.