Set-StrictMode

Establishes and enforces coding rules in expressions, scripts, and script blocks.
Set-StrictMode -Version* <Version> [<CommonParameters>]
Set-StrictMode -Off* [<CommonParameters>]

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.

Parameters
-Off <SwitchParameter>

  • This value is required
  • Default value is None

Indicates that this cmdlet turns strict mode off. This parameter also turns off Set-PSDebug -Strict.

-Version <Version>

  • This value is required
  • Default value is None

Specifies the conditions that cause an error in strict mode.

The acceptable values for this parameter are:

— 1.0

—- Prohibits references to uninitialized variables, except for uninitialized variables in strings.

— 2.0

—- Prohibits references to uninitialized variables. This includes uninitialized variables in strings.—- Prohibits references to non-existent properties of an object.—- Prohibits function calls that use the syntax for calling methods.—- Prohibits a variable without a name (${}).

Latest

—- Selects the latest version available. The latest version is the most strict. Use this value to make sure that scripts use the strictest available version, even when new versions are added to Windows PowerShell.

<CommonParameters>

This cmdlet supports the common parameters: Verbose, Debug,ErrorAction, ErrorVariable, WarningAction, WarningVariable,OutBuffer, PipelineVariable, and OutVariable.

Inputs

None

You cannot pipe input to this cmdlet.

Outputs

None

This cmdlet does not return any output.

Examples
  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 
       + 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.

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

    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

    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.

Additional 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