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Set-StrictMode

Published: February 29, 2012

Updated: August 15, 2012

Applies To: Windows PowerShell 2.0, Windows PowerShell 3.0

Set-StrictMode

Establishes and enforces coding rules in expressions, scripts, and script blocks.

Syntax

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

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




Detailed 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, so 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

Turns strict mode off. This parameter also turns off "Set-PSDebug -Strict".


Aliases

none

Required?

true

Position?

named

Default Value

None

Accept Pipeline Input?

false

Accept Wildcard Characters?

false

-Version<Version>

Specifies the conditions that cause an error in strict mode. This parameter is required.

The valid values are "1.0", "2.0", and "Latest". The following list shows the effect of each value.

1.0

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

2.0

-- Prohibits references to uninitialized variables (including 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 (most strict) version available. Use this value to assure that scripts use the strictest available version, even when new versions are added to Windows PowerShell.


Aliases

none

Required?

true

Position?

named

Default Value

None

Accept Pipeline Input?

false

Accept Wildcard Characters?

false

<CommonParameters>

This cmdlet supports the common parameters: -Verbose, -Debug, -ErrorAction, -ErrorVariable, -OutBuffer, and -OutVariable. For more information, see  about_CommonParameters (http://go.microsoft.com/fwlink/p/?LinkID=113216).

Inputs

The input type is the type of the objects that you can pipe to the cmdlet.

  • None

    You cannot pipe input to this cmdlet.


Outputs

The output type is the type of the objects that the cmdlet emits.

  • None

    This cmdlet does not return any output.


Notes

  • Set-StrictMode is similar to 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.

Examples

-------------------------- EXAMPLE 1 --------------------------

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

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


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

-------------------------- EXAMPLE 2 --------------------------

This command turns strict mode on and sets it to version 2.0. As a result, Windows PowerShell throws an error if you use method syntax (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. With 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. With version 2.0, it is interpreted correctly as a reference error.


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

Related topics


Set-PSDebug

about_Scopes

about_Debuggers



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