AvoidGlobalVars

Severity Level: Warning

Default state: Always enabled

Description

You should avoid modifying global variables in your scripts and functions because other scripts or functions that run in the same session can depend on them. This can lead to unexpected behavior and make it difficult to debug your code.

This rule detects usage of variables with the global scope modifier. PowerShell controls access to variables, functions, aliases, and drives through a mechanism known as scoping. Variables and functions that are present when PowerShell starts were created in the global scope. Globally scoped variables include:

• Automatic variables
• Preference variables

This rule doesn't detect use of the New-Variable cmdlet to create variables in the global scope or the other *-Variable cmdlets to work with variables in the global scope. It only detects variable expressions with the global scope modifier, like $global:example.

This rule doesn't apply to variable expressions that use the global scope modifier where the variable name is for an automatic variable or a preference variable.

Use local or script scope for variables instead of the global scope. To learn more, see about_Scopes.

Example

Noncompliant

$var1 = 'foo'
function Test-NotGlobal ($var) {
    $Global:var1 = $var
}
Test-NotGlobal 'bar'
$var1

Compliant

$var1 = 'foo'
function Test-NotGlobal ($var) {
    $var1 = $var
}
Test-NotGlobal 'bar'
$var1

Configure rule

This rule is always enabled and isn't configurable. Use one of the following methods to avoid using this rule:

• Create a custom rule configuration file to include only the rules you want or exclude the rules you don't want.
• Add the appropriate rule suppression attributes to your code to suppress the rule for specific code blocks. For more information, see the Suppressing rules section of Using PSScriptAnalyzer.