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About Language Modes

JuanPablo Jofre|Last Updated: 11/22/2016
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3 Contributors

about_Language_Modes

SHORT DESCRIPTION

Explains language modes and their effect on Windows PowerShell sessions.

LONG DESCRIPTION

The language mode of a Windows PowerShell session determines, in part, which elements of the Windows PowerShell language can be used in the session.

Windows PowerShell supports the following language modes: -- FullLanguage -- ConstrainedLanguage (introduced in Windows PowerShell 3.0) -- RestrictedLanguage -- NoLanguage

WHAT IS A LANGUAGE MODE?

The language mode determines the language elements that are permitted in the session.

The language mode is actually a property of the session configuration (or "endpoint") that is used to create the session. All sessions that use a particular session configuration have the language mode of the session configuration.

All Windows PowerShell sessions have a language mode, including PSSessions that you create by using the New-PSSession cmdlet, temporary sessions that use the ComputerName parameter, and the default sessions that appear when you start Windows PowerShell.

Remote sessions are created by using the session configurations on the remote computer. The language mode set in the session configuration determines the language mode of the session. To specify the session configuration of a PSSession, use the ConfigurationName parameter of cmdlets that create a session.

LANGUAGE MODES

This section describes the language modes in Windows PowerShell sessions.

FULL LANGUAGE (FullLanguage) The FullLanguage language mode permits all language elements in the session. FullLanguage is the default language mode for default sessions on all versions of Windows except for Windows RT.

RESTRICTED LANGUAGE (RestrictedLanguage) In RestrictedLanguage language mode, users may run commands (cmdlets, functions, CIM commands, and workflows) but are not permitted to use script blocks.

Only the following variables are permitted: -- $PSCulture -- $PSUICulture -- $True -- $False -- $Null.

Only the following comparison operators are permitted: -- -eq (equal) -- -gt (greater-than) -- -lt (less-than)

Assignment statements, property references, and method calls are not permitted.

NO LANGUAGE (NoLanguage) In NoLanguage language mode, users may run commands, but they cannot use any language elements.

CONSTRAINED LANGUAGE (Constrained Language) The ConstrainedLanguage language mode permits all Windows cmdlets and all Windows PowerShell language elements, but it limits permitted types.

ConstrainedLanguage language mode is designed to support User Mode Code Integrity (UMCI) on Windows RT. It is the only supported language mode on Windows RT, but it is available on all supported systems.

UMCI protects ARM devices by allowing only Microsoft- signed and Microsoft-certified apps to be installed on Windows RT-based devices. ConstrainedLanguage mode prevents users from using Windows PowerShell to circumvent or violate UMCI.

The features of ConstrainedLanguage mode are as follows:

-- All cmdlets in Windows modules, and other UMCI-approved cmdlets, are fully functional and have complete access to system resources, except as noted.

-- All elements of the Windows PowerShell scripting language are permitted.

-- All modules included in Windows can be imported and all commands that the modules export run in the session.

-- In Windows PowerShell Workflow, you can write and run script workflows (workflows written in the Windows PowerShell language). XAML-based workflows are not supported and you cannot run XAML in a script workflow, such as by using "Invoke-Expression -Language XAML". Also, workflows cannot call other workflows, although nested workflows are permitted.

-- The Add-Type cmdlet can load signed assemblies, but it cannot load arbitrary C# code or Win32 APIs.

-- The New-Object cmdlet can be used only on allowed types (listed below).

-- Only allowed types (listed below) can be used in Windows PowerShell. Other types are not permitted.

-- Type conversion is permitted, but only when the result is an allowed type.

-- Cmdlet parameters that convert string input to types work only when the resulting type is an allowed type.

-- The ToString() method and the .NET methods of allowed types (listed below) can be invoked. Other methods cannot be invoked.

-- Users can get all properties of allowed types. Users can set the values of properties only on Core types.

-- Only the following COM objects are permitted. -- Scripting.Dictionary -- Scripting.FileSystemObject -- VBScript.RegExp

Allowed Types: The following types are permitted in ConstrainedLanguage language mode. Users can get properties, invoke methods, and convert objects to these types.

AliasAttribute AllowEmptyCollectionAttribute AllowEmptyStringAttribute AllowNullAttribute Array Bool byte char CmdletBindingAttribute DateTime decimal DirectoryEntry DirectorySearcher double float Guid Hashtable int Int16 long ManagementClass ManagementObject ManagementObjectSearcher NullString OutputTypeAttribute ParameterAttribute PSCredential PSDefaultValueAttribute PSListModifier PSObject PSPrimitiveDictionary PSReference PSTypeNameAttribute Regex SByte string SupportsWildcardsAttribute SwitchParameter System.Globalization.CultureInfo System.Net.IPAddress System.Net.Mail.MailAddress System.Numerics.BigInteger System.Security.SecureString TimeSpan UInt16 UInt32 UInt64

FINDING THE LANGUAGE MODE OF A SESSION CONFIGURATION

When a session configuration is created by using a session configuration file, the session configuration has a LanguageMode property. You can find the language mode by getting the value of the LanguageMode property.

PS C:> (Get-PSSessionConfiguration -Name Test).LanguageMode FullLanguage

On other session configurations, you can find the language mode indirectly by finding the language mode of a session that is created by using the session configuration.

FINDING THE LANGUAGE MODE OF A SESSION

You can find the language mode of a FullLanguage or ConstrainedLanguage session by getting the value of the LanguageMode property of the session state.

For example: PS C:> $ExecutionContext.SessionState.LanguageMode ConstrainedLanguage

However, in sessions with RestrictedLanguage and NoLanguage language modes, you cannot use the dot method to get property values. Instead, the error message reveals the language mode.

When you run the $ExecutionContext.SessionState.LanguageMode command in a RestrictedLanguage session, Windows PowerShell returns the PropertyReferenceNotSupportedInDataSection and VariableReferenceNotSupportedInDataSection error messages.

PropertyReferenceNotSupportedInDataSection: Property references are not allowed in restricted language mode or a Data section.

VariableReferenceNotSupportedInDataSection A variable that cannot be referenced in restricted language mode or a Data section is being referenced.

When you run the $ExecutionContext.SessionState.LanguageMode command in a NoLanguage session, Windows PowerShell returns the ScriptsNotAllowed error message.

ScriptsNotAllowed The syntax is not supported by this runspace. This might be because it is in no-language mode.

KEYWORDS

about_ConstrainedLanguage about_FullLanguage about_NoLanguage about_RestrictedLanguage

SEE ALSO

about_Session_ConfigurationFiles about_Session_Configurations about_Windows_RT

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