Set-Strict Mode

Syntax

Set-StrictMode
   -Version <Version>
   [<CommonParameters>]

Set-StrictMode
   [-Off]
   [<CommonParameters>]

Description

The Set-StrictMode cmdlet configures strict mode for the current scope and all child scopes, and turns it on and off. When strict mode is on, Windows PowerShell generates a terminating error when the content of an expression, script, or script block violates basic best-practice coding rules.

Use the Version parameter to determine which coding rules are enforced.

Unlike the Set-PSDebug cmdlet, Set-StrictMode affects only the current scope and its child scopes. Therefore, you can use it in a script or function without affecting the global scope.

When Set-StrictMode is off, uninitialized variables (Version 1) are assumed to have a value of 0 (zero) or $Null, depending on type. References to non-existent properties return $Null, and the results of function syntax that is not valid vary with the error. Unnamed variables are not permitted.

Examples

Example 1: Turn on strict mode as version 1.0

PS C:\> Set-StrictMode -Version 1.0

PS C:\> $a -gt 5

False



The variable $a cannot be retrieved because it has not been set yet.



At line:1 char:3



+ $a <<<<  -gt 5



+ CategoryInfo          : InvalidOperation: (a:Token) [], RuntimeException



+ FullyQualifiedErrorId : VariableIsUndefined

This command turns strict mode on and sets it to version 1.0. As a result, attempts to reference variables that are not initialized fail.

The sample output shows the effect of version 1.0 strict mode.

Example 2: Turn on strict mode as version 2.0

PS C:\> # Set-StrictMode -Version 2.0

# Strict mode is off by default.



PS C:\> function add ($a, $b) {$a + $b}

PS C:\> add 3 4

7

PS C:\> add(3,4)

3

4

PS C:\> Set-StrictMode -Version 2.0

PS C:\> add(3,4)



The function or command was called like a method. Parameters should be separated by spaces, as described in 'Get-Help about_Parameter.'

At line:1 char:4

+ add <<<< (3,4)

+ CategoryInfo          : InvalidOperation: (:) [], RuntimeException

+ FullyQualifiedErrorId : StrictModeFunctionCallWithParens



PS C:\> Set-StrictMode -Off

PS C:\> $string = "This is a string."

PS C:\> $string.Month

PS C:\>

PS C:\> Set-StrictMode -Version 2.0

PS C:\> $string = "This is a string."

PS C:\> $string.Month



Property 'month' cannot be found on this object; make sure it exists.

At line:1 char:9

+ $string. <<<< month

+ CategoryInfo          : InvalidOperation: (.:OperatorToken) [], RuntimeException

+ FullyQualifiedErrorId : PropertyNotFoundStrict

This command turns strict mode on and sets it to version 2.0. As a result, Windows PowerShell returns an error if you use method syntax, which uses parentheses and commas, for a function call or reference uninitialized variables or non-existent properties.

The sample output shows the effect of version 2.0 strict mode.

Without version 2.0 strict mode, the "(3,4)" value is interpreted as a single array object to which nothing is added. By using version 2.0 strict mode, it is correctly interpreted as faulty syntax for submitting two values.

Without version 2.0, the reference to the non-existent Month property of a string returns only $Null. By using version 2.0, it is interpreted correctly as a reference error.

Required Parameters

Inputs

None

You cannot pipe input to this cmdlet.

Outputs

None

This cmdlet does not return any output.

Notes

• Set-StrictMode is like the Strict parameter of Set-PSDebug . Set-StrictMode -Version 1 is equivalent to Set-PSDebug -Strict , except that Set-PSDebug is effective in all scopes. Set-StrictMode is effective only in the scope in which it is set and in its child scopes. For more information about scopes in Windows PowerShell, see about_Scopes.

*

Related Links

• Set-PSDebug