Pipelines

The pipeline is one of the most prominent features of PowerShell. The pipeline is used to send output from one command (standard out or StdOut) into another command (standard in or StdIn).

Standard output

The term standard output is used because there are different kinds of output. Each of these different forms of output is referred to as a stream.

When assigning the output of a command to a variable, the values are taken from the standard output (the output stream) of a command. For example, the following command assigns the data from the standard output to a variable:

$stdout = Get-CimInstance Win32_ComputerSystem

Non-standard output

In PowerShell there are other output streams; these include error (Write-Error), information (Write-Information, introduced in PowerShell 5), warning (Write-Warning), and Verbose (Write-Verbose). PowerShell also has Write-Host, which displays information to the PowerShell host (the console, or PowerShell ISE). Each of these has a stream of its own.

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