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about_Preference_Variables

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Short description

Variables that customize the behavior of PowerShell.

Long description

PowerShell includes a set of variables that enable you to customize its behavior. These preference variables work like the options in GUI-based systems.

The preference variables affect the PowerShell operating environment and all commands run in the environment. In many cases, the cmdlets have parameters that you can use to override the preference behavior for a specific command.

The following table lists the preference variables and their default values.

Variable Default Value
$ConfirmPreference High
$DebugPreference SilentlyContinue
$ErrorActionPreference Continue
$ErrorView NormalView
$FormatEnumerationLimit 4
$InformationPreference SilentlyContinue
$LogCommandHealthEvent $False (not logged)
$LogCommandLifecycleEvent $False (not logged)
$LogEngineHealthEvent $True (logged)
$LogEngineLifecycleEvent $True (logged)
$LogProviderLifecycleEvent $True (logged)
$LogProviderHealthEvent $True (logged)
$MaximumAliasCount 4096
$MaximumDriveCount 4096
$MaximumErrorCount 256
$MaximumFunctionCount 4096
$MaximumHistoryCount 4096
$MaximumVariableCount 4096
$OFS Space character (" ")
$OutputEncoding ASCIIEncoding object
$ProgressPreference Continue
$PSDefaultParameterValues @{} (empty hash table)
$PSEmailServer $Null (none)
$PSModuleAutoLoadingPreference All
$PSSessionApplicationName 'wsman'
$PSSessionConfigurationName 'http://schemas.microsoft.com/powershell/Microsoft.PowerShell'
$PSSessionOption PSSessionOption object
$Transcript $Null (none)
$VerbosePreference SilentlyContinue
$WarningPreference Continue
$WhatIfPreference $False

PowerShell includes the following environment variables that store user preferences. For more information about these environment variables, see about_Environment_Variables.

  • $env:PSExecutionPolicyPreference
  • $env:PSModulePath

Note

Changes to preference variables apply only in the scope they are made and any child scopes thereof. For example, you can limit the effects of changing a preference variable to a single function or script. For more information, see about_Scopes.

Working with preference variables

This document describes each of the preference variables.

To display the current value of a specific preference variable, type the variable's name. For example, the following command displays the $ConfirmPreference variable's value.

 $ConfirmPreference

High

To change a variable's value, use an assignment statement. For example, the following statement changes the $ConfirmPreference parameter's value to Medium.

$ConfirmPreference = "Medium"

The values that you set are specific to the current PowerShell session. To make variables effective in all PowerShell sessions, add them to your PowerShell profile. For more information, see about_Profiles.

Working remotely

When you run commands on a remote computer, the remote commands are only subject to the preferences set in the remote computer's PowerShell client. For example, when you run a remote command, the value of the remote computer's $DebugPreference variable determines how PowerShell responds to debugging messages.

For more information about remote commands, see about_Remote.

$ConfirmPreference

Determines whether PowerShell automatically prompts you for confirmation before running a cmdlet or function.

The $ConfirmPreference variable takes one of the ConfirmImpact enumeration values: High, Medium, Low, or None.

Cmdlets and functions are assigned a risk of High, Medium, or Low. When the value of the $ConfirmPreference variable is less than or equal to the risk assigned to a cmdlet or function, PowerShell automatically prompts you for confirmation before running the cmdlet or function. For more information about assigning a risk to cmdlets or functions, see about_Functions_CmdletBindingAttribute.

If the value of the $ConfirmPreference variable is None, PowerShell never automatically prompts you before running a cmdlet or function.

To change the confirming behavior for all cmdlets and functions in the session, change $ConfirmPreference variable's value.

To override the $ConfirmPreference for a single command, use a cmdlet's or function's Confirm parameter. To request confirmation, use -Confirm. To suppress confirmation, use -Confirm:$false.

Valid values of $ConfirmPreference:

  • None: PowerShell doesn't prompt automatically. To request confirmation of a particular command, use the Confirm parameter of the cmdlet or function.
  • Low: PowerShell prompts for confirmation before running cmdlets or functions with a low, medium, or high risk.
  • Medium: PowerShell prompts for confirmation before running cmdlets or functions with a medium, or high risk.
  • High: PowerShell prompts for confirmation before running cmdlets or functions with a high risk.

Detailed explanation

PowerShell can automatically prompt you for confirmation before doing an action. For example, when cmdlet or function significantly affects the system to delete data or use a significant amount of system resources.

Remove-Item -Path C:\file.txt

Confirm
Are you sure you want to perform this action?
Performing operation "Remove File" on Target "C:\file.txt".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [?] Help (default is "Y"):

The estimate of the risk is an attribute of the cmdlet or function known as its ConfirmImpact. Users can't change it.

Cmdlets and functions that might pose a risk to the system have a Confirm parameter that you can use to request or suppress confirmation for a single command.

Most cmdlets and functions keep the default value of Medium for ConfirmImpact. $ConfirmPreference is set to High by default. Therefore, it's rare that commands automatically prompt for confirmation when users don't specify the Confirm parameter. To extend automatic confirmation prompting to more cmdlets and functions, set the value of $ConfirmPreference to Medium or Low.

Examples

This example shows the effect of the $ConfirmPreference variable's default value, High. The High value only confirms high-risk cmdlets and functions. Since most cmdlets and functions are medium risk, they aren't automatically confirmed and Remove-Item deletes the file. Adding -Confirm to the command prompts the user for confirmation.

$ConfirmPreference

High

Remove-Item -Path C:\temp1.txt

Use -Confirm to request confirmation.

Remove-Item -Path C:\temp2.txt -Confirm

Confirm
Are you sure you want to perform this action?
Performing operation "Remove File" on Target "C:\temp2.txt".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend
[?] Help (default is "Y"):

The following example shows the effect of changing the value of $ConfirmPreference to Medium. Because most cmdlets and function are medium risk, they're automatically confirmed. To suppress the confirmation prompt for a single command, use the Confirm parameter with a value of $false.

$ConfirmPreference = "Medium"
Remove-Item -Path C:\temp2.txt

Confirm
Are you sure you want to perform this action?
Performing operation "Remove File" on Target "C:\temp2.txt".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend
[?] Help (default is "Y"):

Remove-Item -Path C:\temp3.txt -Confirm:$false

$DebugPreference

Determines how PowerShell responds to debugging messages generated by a script, cmdlet or provider, or by a Write-Debug command at the command line.

The $DebugPreference variable takes one of the ActionPreference enumeration values: SilentlyContinue, Stop, Continue, Inquire, Ignore, Suspend, or Break.

Some cmdlets display debugging messages, which are typically technical messages designed for programmers and technical support professionals. By default, debugging messages aren't displayed, but you can display debugging messages by changing the value of $DebugPreference.

You can use the Debug common parameter of a cmdlet to display or hide the debugging messages for a specific command. For more information, see about_CommonParameters.

The valid values are as follows:

  • Stop: Displays the debug message and stops executing. Writes an error to the console.
  • Inquire: Displays the debug message and asks you whether you want to continue.
  • Continue: Displays the debug message and continues with execution.
  • SilentlyContinue: (Default) No effect. The debug message isn't displayed and execution continues without interruption.

Adding the Debug common parameter to a command, when the command is configured to generate a debugging message, changes the value of the $DebugPreference variable to Inquire.

Examples

The following examples show the effect of changing the values of $DebugPreference when a Write-Debug command is entered at the command line. The change affects all debugging messages, including messages generated by cmdlets and scripts. The examples show the Debug parameter, which displays or hides the debugging messages related to a single command.

This example shows the effect of the $DebugPreference variable's default value, SilentlyContinue. By default, the Write-Debug cmdlet's debug message isn't displayed and processing continues. When the Debug parameter is used, it overrides the preference for a single command. The user is prompted for confirmation.

$DebugPreference

SilentlyContinue

Write-Debug -Message "Hello, World"

Write-Debug -Message "Hello, World" -Debug

DEBUG: Hello, World
Confirm
Continue with this operation?
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend
[?] Help (default is "Y"):

This example shows the effect of $DebugPreference with the Continue value. The debug message is displayed and the command continues to process.

$DebugPreference = "Continue"
Write-Debug -Message "Hello, World"

DEBUG: Hello, World

This example uses the Debug parameter with a value of $false to suppress the message for a single command. The debug message isn't displayed.

Write-Debug -Message "Hello, World" -Debug:$false

This example shows the effect of $DebugPreference being set to the Stop value. The debug message is displayed and the command is stopped.

$DebugPreference = "Stop"
Write-Debug -Message "Hello, World"

DEBUG: Hello, World
Write-Debug : The running command stopped because the preference variable
 "DebugPreference" or common parameter is set to Stop: Hello, World
At line:1 char:1
+ Write-Debug -Message "Hello, World"

This example uses the Debug parameter with a value of $false to suppress the message for a single command. The debug message isn't displayed and processing isn't stopped.

Write-Debug -Message "Hello, World" -Debug:$false

This example shows the effect of $DebugPreference being set to the Inquire value. The debug message is displayed and the user is prompted for confirmation.

$DebugPreference = "Inquire"
Write-Debug -Message "Hello, World"

DEBUG: Hello, World

Confirm
Continue with this operation?
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend
[?] Help (default is "Y"):

This example uses the Debug parameter with a value of $false to suppress the message for a single command. The debug message isn't displayed and processing continues.

Write-Debug -Message "Hello, World" -Debug:$false

$ErrorActionPreference

Determines how PowerShell responds to a non-terminating error, an error that doesn't stop the cmdlet processing. For example, at the command line or in a script, cmdlet, or provider, such as the errors generated by the Write-Error cmdlet.

The $ErrorActionPreference variable takes one of the ActionPreference enumeration values: SilentlyContinue, Stop, Continue, Inquire, Ignore, or Suspend.

You can use a cmdlet's ErrorAction common parameter to override the preference for a specific command.

The valid values are as follows:

  • Continue: (Default) Displays the error message and continues executing.
  • Ignore: Suppresses the error message and continues to execute the command. The Ignore value is intended for per-command use, not for use as saved preference. Ignore isn't a valid value for the $ErrorActionPreference variable.
  • Inquire: Displays the error message and asks you whether you want to continue.
  • SilentlyContinue: No effect. The error message isn't displayed and execution continues without interruption.
  • Stop: Displays the error message and stops executing. In addition to the error generated, the Stop value generates an ActionPreferenceStopException object to the error stream.
  • Suspend: Automatically suspends a workflow job to allow for further investigation. After investigation, the workflow can be resumed. The Suspend value is intended for per-command use, not for use as saved preference. Suspend isn't a valid value for the $ErrorActionPreference variable.

$ErrorActionPreference and the ErrorAction parameter don't affect how PowerShell responds to terminating errors that stop cmdlet processing. For more information about the ErrorAction common parameter, see about_CommonParameters.

Examples

These examples show the effect of the different values of the $ErrorActionPreference variable. The ErrorAction parameter is used to override the $ErrorActionPreference value.

This example shows the $ErrorActionPreference default value, Continue. A non-terminating error is generated. The message is displayed and processing continues.

# Change the ErrorActionPreference to 'Continue'
$ErrorActionPreference = 'Continue'
# Generate a non-terminating error and continue processing the script.
Write-Error -Message  'Test Error' ; Write-Host 'Hello World'

Write-Error -Message  'Test Error' ; Write-Host 'Hello World' : Test Error
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException

Hello World

This example shows the $ErrorActionPreference default value, Inquire. An error is generated and a prompt for action is shown.

# Change the ErrorActionPreference to 'Inquire'
$ErrorActionPreference = 'Inquire'
Write-Error -Message 'Test Error' ; Write-Host 'Hello World'

Confirm
Test Error
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend  [?] Help (default is "Y"):

This example shows the $ErrorActionPreference set to SilentlyContinue. The error message is suppressed.

# Change the ErrorActionPreference to 'SilentlyContinue'
$ErrorActionPreference = 'SilentlyContinue'
# Generate an error message
Write-Error -Message 'Test Error' ; Write-Host 'Hello World'
# Error message is suppressed and script continues processing

Hello World

This example shows the $ErrorActionPreference set to Stop. It also shows the extra object generated to the $Error variable.

# Change the ErrorActionPreference to 'Stop'
$ErrorActionPreference = 'Stop'
# Error message is generated and script stops processing
Write-Error -Message 'Test Error' ; Write-Host 'Hello World'

# Show the ActionPreferenceStopException and the error generated
$Error[0]
$Error[1]

Write-Error -Message 'Test Error' ; Write-Host 'Hello World' : Test Error
At line:1 char:1
+ Write-Error -Message 'Test Error' ; Write-Host 'Hello World'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException

The running command stopped because the preference variable "ErrorActionPreference"
or common parameter is set to Stop: Test Error

Write-Error -Message 'Test Error' ; Write-Host 'Hello World' : Test Error
At line:1 char:1
+ Write-Error -Message 'Test Error' ; Write-Host 'Hello World'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException

$ErrorView

Determines the display format of error messages in PowerShell.

The $ErrorView variable takes one of the ErrorView enumeration values: NormalView or CategoryView.

The valid values are as follows:

  • NormalView: A detailed view designed for most users. Consists of a description of the error and the name of the object involved in the error.

  • CategoryView: A succinct, structured view designed for production environments. The format is as follows:

    {Category}: ({TargetName}:{TargetType}):[{Activity}], {Reason}

For more information about the fields in CategoryView, see ErrorCategoryInfo class.

Examples

This example shows how an error appears when the value of $ErrorView is the default, NormalView. Get-ChildItem is used to find a non-existent file.

Get-ChildItem -Path C:\nofile.txt

Get-ChildItem : Cannot find path 'C:\nofile.txt' because it does not exist.
At line:1 char:1
+ Get-ChildItem -Path C:\nofile.txt

This example shows how the same error appears when the value of $ErrorView is changed to CategoryView.

$ErrorView = "CategoryView"
Get-ChildItem -Path C:\nofile.txt

ObjectNotFound: (C:\nofile.txt:String) [Get-ChildItem], ItemNotFoundException

This example demonstrates that the value of $ErrorView only affects the error display. It doesn't change the structure of the error object that's stored in the $Error automatic variable. For information about the $Error automatic variable, see about_automatic_variables.

The following command takes the ErrorRecord object associated with the most recent error in the error array, element 0, and formats the properties of object in a list.

$Error[0] | Format-List -Property * -Force

PSMessageDetails      :
Exception             : System.Management.Automation.ItemNotFoundException:
                          Cannot find path 'C:\nofile.txt' because it does
                          not exist.
                        at System.Management.Automation.SessionStateInternal.
                          GetChildItems(String path, Boolean recurse, UInt32
                          depth, CmdletProviderContext context)
                        at System.Management.Automation.ChildItemCmdlet
                          ProviderIntrinsics.Get(String path, Boolean
                          recurse, UInt32 depth, CmdletProviderContext context)
                        at Microsoft.PowerShell.Commands.GetChildItemCommand.
                          ProcessRecord()
TargetObject          : C:\nofile.txt
CategoryInfo          : ObjectNotFound: (C:\nofile.txt:String) [Get-ChildItem],
                          ItemNotFoundException
FullyQualifiedErrorId : PathNotFound,
                          Microsoft.PowerShell.Commands.GetChildItemCommand
ErrorDetails          :
InvocationInfo        : System.Management.Automation.InvocationInfo
ScriptStackTrace      : at <ScriptBlock>, <No file>: line 1
PipelineIterationInfo : {0, 1}

$FormatEnumerationLimit

Determines how many enumerated items are included in a display. This variable doesn't affect the underlying objects, only the display. When the value of $FormatEnumerationLimit is fewer than the number of enumerated items, PowerShell adds an ellipsis (...) to indicate items not shown.

Valid values: Integers (Int32)

Default value: 4

Examples

This example shows how to use the $FormatEnumerationLimit variable to improve the display of enumerated items.

The command in this example generates a table that lists all the services running on the computer in two groups: one for running services and one for stopped services. It uses a Get-Service command to get all the services, and then sends the results through the pipeline to the Group-Object cmdlet, which groups the results by the service status.

The result is a table that lists the status in the Name column, and the processes in the Group column. To change the column labels, use a hash table, see about_Hash_Tables. For more information, see the examples in Format-Table.

Find the current value of $FormatEnumerationLimit.

$FormatEnumerationLimit

4

List all services grouped by Status. There are a maximum of four services listed in the Group column for each status because $FormatEnumerationLimit has a value of 4.

Get-Service | Group-Object -Property Status

Count  Name       Group
-----  ----       -----
60     Running    {AdtAgent, ALG, Ati HotKey Poller, AudioSrv...}
41     Stopped    {Alerter, AppMgmt, aspnet_state, ATI Smart...}

To increase the number of items listed, increase the value of $FormatEnumerationLimit to 1000. Use Get-Service and Group-Object to display the services.

$FormatEnumerationLimit = 1000
Get-Service | Group-Object -Property Status

Count  Name       Group
-----  ----       -----
60     Running    {AdtAgent, ALG, Ati HotKey Poller, AudioSrv, BITS, CcmExec...
41     Stopped    {Alerter, AppMgmt, aspnet_state, ATI Smart, Browser, CiSvc...

Use Format-Table with the Wrap parameter to display the list of services.

Get-Service | Group-Object -Property Status | Format-Table -Wrap

Count  Name       Group
-----  ----       -----
60     Running    {AdtAgent, ALG, Ati HotKey Poller, AudioSrv, BITS, CcmExec,
                  Client for NFS, CryptSvc, DcomLaunch, Dhcp, dmserver,
                  Dnscache, ERSvc, Eventlog, EventSystem, FwcAgent, helpsvc,
                  HidServ, IISADMIN, InoRPC, InoRT, InoTask, lanmanserver,
                  lanmanworkstation, LmHosts, MDM, Netlogon, Netman, Nla,
                  NtLmSsp, PlugPlay, PolicyAgent, ProtectedStorage, RasMan,
                  RemoteRegistry, RpcSs, SamSs, Schedule, seclogon, SENS,
                  SharedAccess, ShellHWDetection, SMT PSVC, Spooler,
                  srservice, SSDPSRV, stisvc, TapiSrv, TermService, Themes,
                  TrkWks, UMWdf, W32Time, W3SVC, WebClient, winmgmt, wscsvc,
                  wuauserv, WZCSVC, zzInterix}

41     Stopped    {Alerter, AppMgmt, aspnet_state, ATI Smart, Browser, CiSvc,
                  ClipSrv, clr_optimization_v2.0.50727_32, COMSysApp,
                  CronService, dmadmin, FastUserSwitchingCompatibility,
                  HTTPFilter, ImapiService, Mapsvc, Messenger, mnmsrvc,
                  MSDTC, MSIServer, msvsmon80, NetDDE, NetDDEdsdm, NtmsSvc,
                  NVSvc, ose, RasAuto, RDSessMgr, RemoteAccess, RpcLocator,
                  SCardSvr, SwPrv, SysmonLog, TlntSvr, upnphost, UPS, VSS,
                  WmdmPmSN, Wmi, WmiApSrv, xmlprov}

$InformationPreference

The $InformationPreference variable lets you set information stream preferences that you want displayed to users. Specifically, informational messages that you added to commands or scripts by adding the Write-Information cmdlet. If the InformationAction parameter is used, its value overrides the value of the $InformationPreference variable. Write-Information was introduced in PowerShell 5.0.

The $InformationPreference variable takes one of the ActionPreference enumeration values: SilentlyContinue, Stop, Continue, Inquire, Ignore, or Suspend.

The valid values are as follows:

  • Stop: Stops a command or script at an occurrence of the Write-Information command.
  • Inquire: Displays the informational message that you specify in a Write-Information command, then asks whether you want to continue.
  • Continue: Displays the informational message, and continues running.
  • Suspend: Automatically suspends a workflow job after a Write-Information command is carried out, to allow users to see the messages before continuing. The workflow can be resumed at the user's discretion.
  • SilentlyContinue: (Default) No effect. The informational messages aren't displayed, and the script continues without interruption.

$Log*Event

The Log*Event preference variables determine which types of events are written to the PowerShell event log in Event Viewer. By default, only engine and provider events are logged. But, you can use the Log*Event preference variables to customize your log, such as logging events about commands.

The Log*Event preference variables are as follows:

  • $LogCommandHealthEvent: Logs errors and exceptions in command initialization and processing. The default is $false (not logged).
  • $LogCommandLifecycleEvent: Logs the starting and stopping of commands and command pipelines and security exceptions in command discovery. The default is $false (not logged).
  • $LogEngineHealthEvent: Logs errors and failures of sessions. The default is $true (logged).
  • $LogEngineLifecycleEvent: Logs the opening and closing of sessions. The default is $true (logged).
  • $LogProviderHealthEvent: Logs provider errors, such as read and write errors, lookup errors, and invocation errors. The default is $true (logged).
  • $LogProviderLifecycleEvent: Logs adding and removing of PowerShell providers. The default is $true (logged). For information about PowerShell providers, see about_Providers.

To enable a Log*Event, type the variable with a value of $true, for example:

$LogCommandLifeCycleEvent = $true

To disable an event type, type the variable with a value of $false, for example:

$LogCommandLifeCycleEvent = $false

The events that you enable are effective only for the current PowerShell console. To apply the configuration to all consoles, save the variable settings in your PowerShell profile. For more information, see about_Profiles.

$MaximumAliasCount

Determines how many aliases are permitted in a PowerShell session. The default value is 4096 and that should be enough for most uses. You can adjust $MaximumAliasCount to meet your needs.

Valid values: 1024 - 32768 (Int32)

Default: 4096

To count the aliases on your system, type:

(Get-Alias).count

$MaximumDriveCount

Determines how many PowerShell drives are permitted in a given session. For example, file system drives and data stores that are exposed by PowerShell providers and appear as drives, such as the Alias: and HKLM: drives.

Valid values: 1024 - 32768 (Int32)

Default: 4096

To count the aliases on your system, type:

(Get-PSDrive).count

$MaximumErrorCount

Determines how many errors are saved in the error history for the session.

Valid values: 256 - 32768 (Int32)

Default: 256

Objects that represent each retained error are stored in the $Error automatic variable. $Error contains an array of error record objects. The most recent error is the first object in the array, $Error[0].

To count the errors on your system, use the $Error array's Count property.

$Error.count

To display a specific error, use the [0] array notation to see the most recent error.

$Error[0]

To display the oldest retained error, type:

$Error[-1]

The Force parameter overrides the special formatting of ErrorRecord objects and reverts to the conventional format. To display the properties of the ErrorRecord object, type the following command:

$Error[0] | Format-List -Property * -Force

In this example, $Error.Count displays the number of errors. To delete all errors from the error history, use the Clear method of the error array.

$Error.Count

17

$Error.Clear()
$Error.Count

0

To find all properties and methods of an error array, use the Get-Member cmdlet with its InputObject parameter. When you use the InputObject parameter, Get-Member displays the properties and methods of the collection.

Get-Member -InputObject $Error

When you pipe a collection of objects to Get-Member, Get-Member displays the properties and methods of the objects in the collection.

$Error | Get-Member

$MaximumFunctionCount

Determines how many functions are permitted in a given session.

Valid values: 1024 - 32768 (Int32)

Default: 4096

To see the functions in your session, use the PowerShell Function: drive that is exposed by the PowerShell Function provider. For more information about the Function provider, about_Function_Provider.

To list the functions in the current session, type:

Get-ChildItem Function:

To count the functions in the current session, type:

(Get-ChildItem Function:).Count

$MaximumHistoryCount

Determines how many commands are saved in the command history for the current session.

Valid values: 1 - 32768 (Int32)

Default: 4096

To determine the number of commands current saved in the command history, type:

(Get-History).Count

To see the commands saved in your session history, use the Get-History cmdlet. For more information, see about_History.

$MaximumVariableCount

Determines how many variables are permitted in a given session, including automatic variables, preference variables, and the variables that you create in commands and scripts.

Valid values: 1024 - 32768 (Int32)

Default: 4096

To see the variables in your session, use the Get-Variable cmdlet and the features of the PowerShell Variable: drive and the PowerShell Variable provider. For information, see about_Variable_Provider.

To find the current number of variables on the system, type:

(Get-Variable).Count

$OFS

The Output Field Separator (OFS) specifies the character that separates the elements of an array that's converted to a string.

Valid values: Any string.

Default: Space

By default, the $OFS variable doesn't exist and the output file separator is a space, but you can add this variable and set it to any string. You can change the value of $OFS in your session, by typing $OFS="<value>".

Note

If you're expecting the default value of a space (" ") in your script, module, or configuration output, be careful that the $OFS default value hasn't been changed elsewhere in your code.

Examples

This example shows that a space is used to separate the values when an array is converted to a string. In this case, an array of integers is stored in a variable and then the variable is cast as a string.

$array = 1,2,3,4
[string]$array

1 2 3 4

To change the separator, add the $OFS variable by assigning a value to it. The variable must be named $OFS.

$OFS = "+"
[string]$array

1+2+3+4

To restore the default behavior, you can assign a space (" ") to the value of $OFS or delete the variable. The following commands delete the variable and then verify that the separator is a space.

Remove-Variable OFS
[string]$array

1 2 3 4

$OutputEncoding

Determines the character encoding method that PowerShell uses when piping data into native applications.

Note

In the majority of scenarios, the value for $OutputEncoding should align to the value of [Console]::InputEncoding.

The valid values are as follows: Objects derived from an Encoding class, such as ASCIIEncoding, UTF7Encoding, UTF8Encoding, UTF32Encoding, and UnicodeEncoding.

Default: ASCIIEncoding object.

Examples

The first command finds the value of $OutputEncoding. Because the value is an encoding object, display only its EncodingName property.

$OutputEncoding.EncodingName

The remaining examples use the following PowerShell script saved as hexdump.ps1 to illustrate the behavior of $OutputEncoding.

$inputStream = [Console]::OpenStandardInput()
try {
    $buffer = [byte[]]::new(1024)
    $read = $inputStream.Read($buffer, 0, $buffer.Length)
    $actual = [byte[]]::new($read)
    [Array]::Copy($buffer, $actual, $read)
    Format-Hex -InputObject $actual
} finally {
    $inputStream.Dispose()
}

The following example shows how the string value café is encoded to bytes when piped into hexdump.ps1 created above. It demonstrates that the string value is encoded using the windows-1252 encoding scheme which is the default encoding on the system tested in question.

'café' | powershell.exe -File .\hexdump.ps1

           00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000   63 61 66 3F 0D 0A                                caf?..

The following example shows how the bytes change when changing the encoding to UTF-8. The é instead of being encoded to 0x3F as done by windows-1252 it will now become 0xC3 0xA9 due to the UTF-8 encoding being used.

$OutputEncoding = [System.Text.UTF8Encoding]::new()
'café' | powershell.exe -File .\hexdump.ps1

           00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000   63 61 66 C3 A9 0D 0A                             café..

$ProgressPreference

Determines how PowerShell responds to progress updates generated by a script, cmdlet, or provider, such as the progress bars generated by the Write-Progress cmdlet. The Write-Progress cmdlet creates progress bars that show a command's status.

The $ProgressPreference variable takes one of the ActionPreference enumeration values: SilentlyContinue, Stop, Continue, Inquire, Ignore, or Suspend.

The valid values are as follows:

  • Stop: Doesn't display the progress bar. Instead, it displays an error message and stops executing.
  • Inquire: Doesn't display the progress bar. Prompts for permission to continue. If you reply with Y or A, it displays the progress bar.
  • Continue: (Default) Displays the progress bar and continues with execution.
  • SilentlyContinue: Executes the command, but doesn't display the progress bar.

$PSDefaultParameterValues

Specifies default values for the parameters of cmdlets and advanced functions. The value of $PSDefaultParameterValues is a hash table where the key consists of the cmdlet name and parameter name separated by a colon (:). The value is a custom default value that you specify.

$PSDefaultParameterValues was introduced in PowerShell 3.0.

For more information about this preference variable, see about_Parameters_Default_Values.

$PSEmailServer

Specifies the default email server that's used to send email messages. This preference variable is used by cmdlets that send email, such as the Send-MailMessage cmdlet.

$PSModuleAutoloadingPreference

Enables and disables automatic importing of modules in the session. The $PSModuleAutoloadingPreference variable doesn't exist by default. The default behavior when the variable isn't defined is the same as $PSModuleAutoloadingPreference = 'All'.

To automatically import a module, get or use a command contained in the module.

The $PSModuleAutoloadingPreference variable takes one of the PSModuleAutoLoadingPreference enumeration values:

  • All: Modules are imported automatically on first-use.
  • ModuleQualified: Modules are imported automatically only when a user uses the module-qualified name of a command in the module. For example, if the user types MyModule\MyCommand, PowerShell imports the MyModule module.
  • None: Disables the automatic importing of modules. To import a module, use the Import-Module cmdlet.

For more information about automatic importing of modules, see about_Modules.

$PSSessionApplicationName

Specifies the default application name for a remote command that uses Web Services for Management (WS-Management) technology. For more information, see About Windows Remote Management.

The system default application name is WSMAN, but you can use this preference variable to change the default.

The application name is the last node in a connection URI. For example, the application name in the following sample URI is WSMAN.

http://Server01:8080/WSMAN

The default application name is used when the remote command doesn't specify a connection URI or an application name.

The WinRM service uses the application name to select a listener to service the connection request. The parameter's value should match the value of the URLPrefix property of a listener on the remote computer.

To override the system default and the value of this variable, and select a different application name for a particular session, use the ConnectionURI or ApplicationName parameters of the New-PSSession, Enter-PSSession, or Invoke-Command cmdlets.

The $PSSessionApplicationName preference variable is set on the local computer, but it specifies a listener on the remote computer. If the application name that you specify doesn't exist on the remote computer, the command to establish the session fails.

$PSSessionConfigurationName

Specifies the default session configuration that's used to create new sessions in the current session.

This preference variable is set on the local computer, but it specifies a session configuration that's located on the remote computer.

The value of the $PSSessionConfigurationName variable is a fully qualified resource URI.

The default value http://schemas.microsoft.com/PowerShell/microsoft.PowerShell indicates the Microsoft.PowerShell session configuration on the remote computer.

If you specify only a configuration name, the following schema URI is prepended:

http://schemas.microsoft.com/PowerShell/

You can override the default and select a different session configuration for a particular session by using the ConfigurationName parameter of the New-PSSession, Enter-PSSession, or Invoke-Command cmdlets.

You can change the value of this variable at any time. When you do, remember that the session configuration that you select must exist on the remote computer. If it doesn't, the command to create a session that uses the session configuration fails.

This preference variable doesn't determine which local session configurations are used when remote users create a session that connects to this computer. However, you can use the permissions for the local session configurations to determine which users may use them.

$PSSessionOption

Establishes the default values for advanced user options in a remote session. These option preferences override the system default values for session options.

The $PSSessionOption variable contains a PSSessionOption object. For more information, see System.Management.Automation.Remoting.PSSessionOption. Each property of the object represents a session option. For example, the NoCompression property turns of data compression during the session.

By default, the $PSSessionOption variable contains a PSSessionOption object with the default values for all options, as shown below.

MaximumConnectionRedirectionCount : 5
NoCompression                     : False
NoMachineProfile                  : False
ProxyAccessType                   : None
ProxyAuthentication               : Negotiate
ProxyCredential                   :
SkipCACheck                       : False
SkipCNCheck                       : False
SkipRevocationCheck               : False
OperationTimeout                  : 00:03:00
NoEncryption                      : False
UseUTF16                          : False
IncludePortInSPN                  : False
OutputBufferingMode               : None
Culture                           :
UICulture                         :
MaximumReceivedDataSizePerCommand :
MaximumReceivedObjectSize         : 209715200
ApplicationArguments              :
OpenTimeout                       : 00:03:00
CancelTimeout                     : 00:01:00
IdleTimeout                       : -00:00:00.0010000

For descriptions of these options and more information, see New-PSSessionOption. For more information about remote commands and sessions, see about_Remote and about_PSSessions.

To change the value of the $PSSessionOption preference variable, use the New-PSSessionOption cmdlet to create a PSSessionOption object with the option values you prefer. Save the output in a variable called $PSSessionOption.

$PSSessionOption = New-PSSessionOption -NoCompression

To use the $PSSessionOption preference variable in every PowerShell session, add a New-PSSessionOption command that creates the $PSSessionOption variable to your PowerShell profile. For more information, see about_Profiles.

You can set custom options for a particular remote session. The options that you set take precedence over the system defaults and the value of the $PSSessionOption preference variable.

To set custom session options, use the New-PSSessionOption cmdlet to create a PSSessionOption object. Then, use the PSSessionOption object as the value of the SessionOption parameter in cmdlets that create a session, such as New-PSSession, Enter-PSSession, and Invoke-Command.

$Transcript

Used by Start-Transcript to specify the name and location of the transcript file. If you don't specify a value for the Path parameter, Start-Transcript uses the path in the value of the $Transcript global variable. If you haven't created this variable, Start-Transcript stores the transcripts in the following location using the default name.

  • Default location: $HOME\Documents
  • Default filename: PowerShell_transcript.<computername>.<random>.<timestamp>.txt

$VerbosePreference

Determines how PowerShell responds to verbose messages generated by a script, cmdlet, or provider, such as the messages generated by the Write-Verbose cmdlet. Verbose messages describe the actions performed to execute a command.

By default, verbose messages aren't displayed, but you can change this behavior by changing the value of $VerbosePreference.

The $VerbosePreference variable takes one of the ActionPreference enumeration values: SilentlyContinue, Stop, Continue, Inquire, Ignore, or Suspend.

The valid values are as follows:

  • Stop: Displays the verbose message and an error message and then stops executing.
  • Inquire: Displays the verbose message and then displays a prompt that asks you whether you want to continue.
  • Continue: Displays the verbose message and then continues with execution.
  • SilentlyContinue: (Default) Doesn't display the verbose message. Continues executing.

You can use the Verbose common parameter of a cmdlet to display or hide the verbose messages for a specific command. For more information, see about_CommonParameters.

Examples

These examples show the effect of the different values of $VerbosePreference and the Verbose parameter to override the preference value.

This example shows the effect of the SilentlyContinue value, that's the default. The command uses the Message parameter, but doesn't write a message to the PowerShell console.

Write-Verbose -Message "Verbose message test."

When the Verbose parameter is used, the message is written.

Write-Verbose -Message "Verbose message test." -Verbose

VERBOSE: Verbose message test.

This example shows the effect of the Continue value. The $VerbosePreference variable is set to Continue and the message is displayed.

$VerbosePreference = "Continue"
Write-Verbose -Message "Verbose message test."

VERBOSE: Verbose message test.

This example uses the Verbose parameter with a value of $false that overrides the Continue value. The message isn't displayed.

Write-Verbose -Message "Verbose message test." -Verbose:$false

This example shows the effect of the Stop value. The $VerbosePreference variable is set to Stop and the message is displayed. The command is stopped.

$VerbosePreference = "Stop"
Write-Verbose -Message "Verbose message test."

VERBOSE: Verbose message test.
Write-Verbose : The running command stopped because the preference variable
  "VerbosePreference" or common parameter is set to Stop: Verbose message test.
At line:1 char:1
+ Write-Verbose -Message "Verbose message test."

This example uses the Verbose parameter with a value of $false that overrides the Stop value. The message isn't displayed.

Write-Verbose -Message "Verbose message test." -Verbose:$false

This example shows the effect of the Inquire value. The $VerbosePreference variable is set to Inquire. The message is displayed and the user is prompted for confirmation.

$VerbosePreference = "Inquire"
Write-Verbose -Message "Verbose message test."

VERBOSE: Verbose message test.

Confirm
Continue with this operation?
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend
[?] Help (default is "Y"):

This example uses the Verbose parameter with a value of $false that overrides the Inquire value. The user isn't prompted and the message isn't displayed.

Write-Verbose -Message "Verbose message test." -Verbose:$false

$WarningPreference

Determines how PowerShell responds to warning messages generated by a script, cmdlet, or provider, such as the messages generated by the Write-Warning cmdlet.

By default, warning messages are displayed and execution continues, but you can change this behavior by changing the value of $WarningPreference.

The $WarningPreference variable takes one of the ActionPreference enumeration values: SilentlyContinue, Stop, Continue, Inquire, Ignore, or Suspend.

The valid values are as follows:

  • Stop: Displays the warning message and an error message and then stops executing.
  • Inquire: Displays the warning message and then prompts for permission to continue.
  • Continue: (Default) Displays the warning message and then continues executing.
  • SilentlyContinue: Doesn't display the warning message. Continues executing.

You can use the WarningAction common parameter of a cmdlet to determine how PowerShell responds to warnings from a particular command. For more information, see about_CommonParameters.

Examples

These examples show the effect of the different values of $WarningPreference. The WarningAction parameter overrides the preference value.

This example shows the effect of the default value, Continue.

$m = "This action can delete data."
Write-Warning -Message $m

WARNING: This action can delete data.

This example uses the WarningAction parameter with the value SilentlyContinue to suppress the warning. The message isn't displayed.

$m = "This action can delete data."
Write-Warning -Message $m -WarningAction SilentlyContinue

This example changes the $WarningPreference variable to the SilentlyContinue value. The message isn't displayed.

$WarningPreference = "SilentlyContinue"
$m = "This action can delete data."
Write-Warning -Message $m

This example uses the WarningAction parameter to stop when a warning is generated.

$m = "This action can delete data."
Write-Warning -Message $m -WarningAction Stop

WARNING: This action can delete data.
Write-Warning : The running command stopped because the preference variable
  "WarningPreference" or common parameter is set to Stop:
    This action can delete data.
At line:1 char:1
+ Write-Warning -Message $m -WarningAction Stop

This example changes the $WarningPreference variable to the Inquire value. The user is prompted for confirmation.

$WarningPreference = "Inquire"
$m = "This action can delete data."
Write-Warning -Message $m

WARNING: This action can delete data.

Confirm
Continue with this operation?
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend
[?] Help (default is "Y"):

This example uses the WarningAction parameter with the value SilentlyContinue. The command continues to execute and no message is displayed.

$m = "This action can delete data."
Write-Warning -Message $m -WarningAction SilentlyContinue

This example changes the $WarningPreference value to Stop.

$WarningPreference = "Stop"
$m = "This action can delete data."
Write-Warning -Message $m

WARNING: This action can delete data.
Write-Warning : The running command stopped because the preference variable
  "WarningPreference" or common parameter is set to Stop:
    This action can delete data.
At line:1 char:1
+ Write-Warning -Message $m

This example uses the WarningAction with the Inquire value. The user is prompted when a warning occurs.

$m = "This action can delete data."
Write-Warning -Message $m -WarningAction Inquire

WARNING: This action can delete data.

Confirm
Continue with this operation?
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend
[?] Help (default is "Y"):

$WhatIfPreference

Determines whether WhatIf is automatically enabled for every command that supports it. When WhatIf is enabled, the cmdlet reports the expected effect of the command, but doesn't execute the command.

The valid values are as follows:

  • False (0, not enabled): (Default) WhatIf isn't automatically enabled. To enable it manually, use the cmdlet's WhatIf parameter.
  • True (1, enabled): WhatIf is automatically enabled on any command that supports it. Users can use the WhatIf parameter with a value of False to disable it manually, such as -WhatIf:$false.

Examples

These examples show the effect of the different values of $WhatIfPreference. They show how to use the WhatIf parameter to override the preference value for a specific command.

This example shows the effect of the $WhatIfPreference variable set to the default value, False. Use Get-ChildItem to verify that the file exists. Remove-Item deletes the file. After the file is deleted, you can verify the deletion with Get-ChildItem.

Get-ChildItem -Path .\test.txt
Remove-Item -Path ./test.txt

    Directory: C:\Test

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---           9/13/2019    10:53             10 test.txt

Get-ChildItem -Path .\test.txt

Get-ChildItem : Cannot find path 'C:\Test\test.txt' because it does not exist.
At line:1 char:1
+ Get-ChildItem -File test.txt

This example shows the effect of using the WhatIf parameter when the value of $WhatIfPreference is False.

Verify that the file exists.

Get-ChildItem -Path .\test2.txt

    Directory: C:\Test

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---           2/28/2019    17:06             12 test2.txt

Use the WhatIf parameter to determine the result of attempting to delete the file.

Remove-Item -Path .\test2.txt -WhatIf

What if: Performing the operation "Remove File" on target "C:\Test\test2.txt".

Verify that the file wasn't deleted.

Get-ChildItem -Path .\test2.txt

    Directory: C:\Test

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---           2/28/2019    17:06             12 test2.txt

This example shows the effect of the $WhatIfPreference variable set to the value, True. When you use Remove-Item to delete a file, the file's path is displayed, but the file isn't deleted.

Attempt to delete a file. A message is displayed about what would happen if Remove-Item was run, but the file isn't deleted.

$WhatIfPreference = "True"
Remove-Item -Path .\test2.txt

What if: Performing the operation "Remove File" on target "C:\Test\test2.txt".

Use Get-ChildItem to verify that the file wasn't deleted.

Get-ChildItem -Path .\test2.txt

    Directory: C:\Test

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---           2/28/2019    17:06             12 test2.txt

This example shows how to delete a file when the value of $WhatIfPreference is True. It uses the WhatIf parameter with a value of $false. Use Get-ChildItem to verify the file was deleted.

Remove-Item -Path .\test2.txt -WhatIf:$false
Get-ChildItem -Path .\test2.txt

Get-ChildItem : Cannot find path 'C:\Test\test2.txt' because it does not exist.
At line:1 char:1
+ Get-ChildItem -Path .\test2.txt

The following are examples of the Get-Process cmdlet that doesn't support WhatIf and Stop-Process that does support WhatIf. The $WhatIfPreference variable's value is True.

Get-Process doesn't support WhatIf. When the command is executed, it displays the Winword process.

Get-Process -Name Winword

 NPM(K)    PM(M)      WS(M)     CPU(s)      Id  SI ProcessName
 ------    -----      -----     ------      --  -- -----------
    130   119.84     173.38       8.39   15024   4 WINWORD

Stop-Process does support WhatIf. The Winword process isn't stopped.

Stop-Process -Name Winword

What if: Performing the operation "Stop-Process" on target "WINWORD (15024)".

You can override the Stop-Process WhatIf behavior using the WhatIf parameter with a value of $false. The Winword process is stopped.

Stop-Process -Name Winword -WhatIf:$false

To verify that the Winword process was stopped, use Get-Process.

Get-Process -Name Winword

Get-Process : Cannot find a process with the name "Winword".
  Verify the process name and call the cmdlet again.
At line:1 char:1
+ Get-Process -Name Winword

See also