AvoidAssignmentToAutomaticVariable.md

AvoidAssignmentToAutomaticVariable

Severity Level: Warning

Description

PowerShell exposes some of its built-in variables that are known as automatic variables. Many of them are read-only and PowerShell would throw an error when trying to assign an value on those. Other automatic variables should only be assigned to in certain special cases to achieve a certain effect as a special technique.

To understand more about automatic variables, see Get-Help about_Automatic_Variables.

How

Use variable names in functions or their parameters that do not conflict with automatic variables.

Example

Wrong

The variable $Error is an automatic variables that exists in the global scope and should therefore never be used as a variable or parameter name.

function foo($Error){ }

function Get-CustomErrorMessage($ErrorMessage){ $Error = "Error occurred: $ErrorMessage" }

Correct

function Get-CustomErrorMessage($ErrorMessage){ $FinalErrorMessage = "Error occurred: $ErrorMessage" }