Automatic variables ($_, $PSVersionTable) in PowerShell

Introduction

Automatic variables in PowerShell hold special information that helps scripts run smoothly without extra setup.

When processing items in a list or pipeline and you want to refer to the current item easily.

When you need to check the version of PowerShell running your script.

When writing quick scripts that handle data flowing through commands without naming variables.

When debugging or logging to see environment details like PowerShell version.

Syntax

PowerShell

$_
$PSVersionTable

$_ represents the current object in the pipeline.

$PSVersionTable is a read-only table showing PowerShell version details.

Examples

This filters processes using more than 100 CPU units, using $_ to refer to each process.

PowerShell

Get-Process | Where-Object { $_.CPU -gt 100 }

This prints the PowerShell version number.

PowerShell

Write-Output $PSVersionTable.PSVersion

Prints the name of each service using $_ inside a loop.

PowerShell

Get-Service | ForEach-Object { "Service: $_.Name" }

Sample Program

This script first shows PowerShell version info, then lists all running services by using $PSVersionTable and $_.

PowerShell

Write-Output "PowerShell version info:"
Write-Output $PSVersionTable

"List of running services with status:" | Write-Output
Get-Service | Where-Object { $_.Status -eq 'Running' } | ForEach-Object { Write-Output "Service: $_.Name" }

Important Notes

$_ only works inside commands that process pipeline input like ForEach-Object or Where-Object.

$PSVersionTable is useful to check compatibility before running scripts.

Summary

$_ is the current item in a pipeline, making it easy to work with each piece of data.

$PSVersionTable shows details about your PowerShell version and environment.

These automatic variables help write shorter, clearer scripts without extra setup.