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about_Preference_Variables

About Preference Variables

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 = (None - empty hash table)
  • $PSEmailServer = (None)
  • $PSModuleAutoLoadingPreference= All
  • $PSSessionApplicationName = WSMAN
  • $PSSessionConfigurationName = http://schemas.microsoft.com/PowerShell/microsoft.PowerShell
  • $PSSessionOption = (See below)
  • $VerbosePreference = SilentlyContinue
  • $WarningPreference = Continue
  • $WhatIfPreference = 0

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

  • PSExecutionPolicyPreference
  • PSModulePath

WORKING WITH PREFERENCE VARIABLES

This document describes each of the preference variables.

To display the current value of a specific preference variable, type the name of the variable. In response, PowerShell provides the value. For example, the following command displays the value of the $ConfirmPreference variable.

PS> $ConfirmPreference
High

To change the value of a variable, use an assignment statement. For example, the following statement assigns the value "Medium" to the $ConfirmPreference variable.

PS> $ConfirmPreference = "Medium"

Like all variables, the values that you set are specific to the current PowerShell session. To make them effective in all Windows PowerShell session, 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 subject only to the preferences set in the PowerShell client on the remote computer. For example, when you run a remote command, the value of the $DebugPreference variable on remote computer determines how Windows 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.

When the value of the $ConfirmPreference variable (High, Medium, Low) is less than or equal to the risk assigned to the cmdlet or function (High, Medium, Low), PowerShell automatically prompts you for confirmation before running the cmdlet or function.

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 the value of the $ConfirmPreference variable.

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

Valid values of $ConfirmPreference:

  • None: PowerShell does not 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

When the actions of a cmdlet or function significantly affect the system, such as those that delete data or use a significant amount of system resources, PowerShell can automatically prompt you for confirmation before performing the action.

For example,

PS> remove-item 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  [S] Suspend
[?] Help (default is "Y"):

The estimate of the risk is an attribute of the cmdlet or function known as its "ConfirmImpact". Users cannot 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.

Because most cmdlets and functions use the default risk value (ConfirmImpact) of Medium, and the default value of $ConfirmPreference is High, automatic confirmation rarely occurs. However, you can activate automatic confirmation by changing the value of $ConfirmPreference to Medium or Low.

EXAMPLES

This example shows the effect of the default value of $ConfirmPreference. The High value only confirms high-risk cmdlets and functions. Since most cmdlets and functions are medium risk, they are not automatically confirmed.

PS> $confirmpreference              #Get the current value of the variable
High

PS> remove-item temp1.txt           #Delete a file
PS>                                 #Deleted without confirmation

PS> remove-item temp2.txt -confirm  #Use to request confirmation

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 are automatically confirmed. To suppress the confirmation prompt for a single command, use the Confirm parameter with a value of $false

PS> $confirmpreference = "Medium"  #Change the value of $ConfirmPreference
PS> remove-item temp2.txt          #Deleting a file triggers confirmation

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"):

PS> remove-item temp3.txt -confirm:$false   #Use to suppress confirmation
PS>

$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.

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

You can also use the Debug common parameter of a cmdlet to display or hide the debugging messages for a specific command. For more information, type: get-help about_commonparameters.

Valid values:

  • 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. Note that 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.

  • Continue: Displays the debug message and continues with execution.

  • SilentlyContinue: No effect. The debug message is not (Default) displayed and execution continues without interruption.

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 those generated by cmdlets and scripts. The examples also show the use of the Debug common parameter, which displays or hides the debugging messages related to a single command.

This example shows the effect of the default value, "SilentlyContinue." The debug message is not displayed and processing continues. The final command uses the Debug parameter to override the preference for a single command.

PS> $debugpreference    # Get the current value of $DebugPreference
SilentlyContinue

PS> write-debug "Hello, World"
PS> # The debug message is not displayed.

PS> # Use the Debug parameter to display message and request confirmation
PS> write-debug "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 the "Continue" value. The final command uses the Debug parameter with a value of $false to suppress the message for a single command.

PS> $debugpreference = "Continue"   # Change the value to "Continue"

PS> write-debug "Hello, World"
DEBUG: Hello, World  # Display message and continue processing.

PS> # Use the Debug parameter with false.
PS> write-debug "Hello, World" -Debug:$false
PS> # The debug message is not displayed.

This example shows the effect of the "Stop" value. The final command uses the Debug parameter with a value of $false to suppress the message for a single command.

PS> $debugpreference = "Stop"       #Change the value to "Stop"
PS> write-debug "Hello, World"
DEBUG: Hello, World
Write-Debug : Command execution stopped because the shell variable "Debug
Preference" is set to Stop.
At line:1 char:12
+ write-debug  <<<< "Hello, World"

PS> # Use the Debug parameter with $false
PS> write-debug "Hello, World" -Debug:$false
PS> # The debug message is not displayed and processing is not stopped.

This example shows the effect of the "Inquire" value. The final command uses the Debug parameter with a value of $false to suppress the message for a single command.

PS> $debugpreference = "Inquire"
PS> write-debug "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"):

PS> # Use the Debug parameter with $false
PS> write-debug "Hello, World" -Debug:$false
PS> # The debug message is not displayed and processing continues.

$ErrorActionPreference

Determines how PowerShell responds to a non-terminating error (an error that does not stop the cmdlet processing) at the command line or in a script, cmdlet, or provider, such as the errors generated by the Write-Error cmdlet.

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

Valid values:

  • Stop: Displays the error message and stops executing.
  • Inquire: Displays the error message and asks you whether you want to continue.
  • Continue: Displays the error message and continues (Default) executing.
  • Suspend: Automatically suspends a workflow job to allow for further investigation. After investigation, the workflow can be resumed.
  • SilentlyContinue: No effect. The error message is not displayed and execution continues without interruption.

NOTE: The Ignore value of the ErrorAction common parameter is not a valid value of the $ErrorActionPreference variable. The Ignore value is intended for per-command use, not for use as saved preference.

Neither $ErrorActionPreference nor the ErrorAction common parameter affect how PowerShell responds to terminating errors (those 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 $ErrorActionPreference and the use of the ErrorAction common parameter to override the preference for a single command. The ErrorAction parameter has the same valid values as the $ErrorActionPreference variable.

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

PS> # Display the value of the preference.
PS> $erroractionpreference
Continue

PS> # Generate a non-terminating error.
PS> write-error "Hello, World"

PS> # The error message is displayed and execution continues.
PS> write-error "Hello, World" : Hello, World

PS> # Use the ErrorAction parameter with a value of "SilentlyContinue".
PS> write-error "Hello, World" -ErrorAction:SilentlyContinue
PS>          # The error message is not displayed and execution continues.

This example shows the effect of the SilentlyContinue value.

PS> # Change the value of the preference.
PS> $ErrorActionPreference = "SilentlyContinue"

PS> # Generate an error message.
PS> write-error "Hello, World"
PS> # Error message is suppressed.

PS> # Use the ErrorAction parameter with a value of "Continue".
PS> write-error "Hello, World" -erroraction:continue

PS> # The error message is displayed and execution continues.
write-error "Hello, World" -erroraction:continue : Hello, World

This example shows the effect of a real error. In this case, the command gets a non-existent file, nofile.txt. The example also uses the ErrorAction common parameter to override the preference.

PS> $erroractionpreference
SilentlyContinue        # Display the value of the preference.

PS> get-childitem -path nofile.txt
PS>                     # Error message is suppressed.

PS> # Change the value to Continue.
PS> $ErrorActionPreference = "Continue"

PS> get-childitem -path nofile.txt
Get-ChildItem : Cannot find path 'C:\nofile.txt' because it does not exist.
At line:1 char:4
+ get-childitem  <<<< nofile.txt

PS> # Use the ErrorAction parameter
PS> get-childitem -path nofile.txt -erroraction SilentlyContinue
PS> # Error message is suppressed.

PS> # Change the value to Inquire.
PS> $ErrorActionPreference = "Inquire"
PS> get-childitem -path nofile.txt

Confirm
Cannot find path 'C:\nofile.txt' because it does not exist.
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend
[?] Help (default is "Y"): y

Get-ChildItem : Cannot find path 'C:\nofile.txt' because it does not exist.
At line:1 char:4
+ get-childitem  <<<< nofile.txt

PS> # Change the value to Continue.
PS> $ErrorActionPreference = "Continue"
PS> Get-Childitem nofile.txt -erroraction "Inquire"
PS> # Use the ErrorAction parameter to override the preference value.

Confirm
Cannot find path 'C:\nofile.txt' because it does not exist.
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend
[?] Help (default is "Y"):

$ErrorView

Determines the display format of error messages in PowerShell.

Valid values:

  • NormalView: A detailed view designed for most users. (default) Consists of a description of the error, the name of the object involved in the error, and arrows (<<<<) that point to the words in the command that caused the error.

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

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

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

EXAMPLES

These example show the effect of the ErrorView values.

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

PS> $ErrorView                         # Verify the value.
NormalView

PS> get-childitem nofile.txt           # Find a non-existent file.
Get-ChildItem : Cannot find path 'C:\nofile.txt' because it does not exist.
At line:1 char:14
+ get-childitem  <<<< nofile.txt

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

PS> $ErrorView = "CategoryView"        # Change the value to
CategoryView

PS> get-childitem nofile.txt
ObjectNotFound: (C:\nofile.txt:String) [Get-ChildItem], ItemNotFoundExcep
tion

This example demonstrates that the value of ErrorView only affects the error display; it does not change the structure of the error object that is stored in the $error automatic variable. For information about the $error automatic variable, see about_automatic_variables.

This command takes the ErrorRecord object associated with the most recent error in the error array (element 0) and formats all of the properties of the error object in a list.

PS> $error[0] | format-list -property * -force

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, CmdletProviderContext context)
at System.Management.Automation.ChildItemCmdletProviderIntrinsics.Get(Stri
ng path,Boolean recurse, CmdletProviderContext context)
at Microsoft.PowerShell.Commands.GetChildItemCommand.ProcessRecord()
TargetObject          : C:\nofile.txt
CategoryInfo          : ObjectNotFound: (C:\nofile.txt:String) [Get-ChildI
tem],ItemNotFoundException
FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetChil
dItemCommand
ErrorDetails          :
InvocationInfo        : System.Management.Automation.InvocationInfo

$FormatEnumerationLimit

Determines how many enumerated items are included in a display. This variable does not affect the underlying objects; just the display. When the value of $FormatEnumerationLimit is less 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 of 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 of the services, and then send the results through the pipeline to the Group-Object cmdlet, which groups the results by the service status.

The resulting display is a table that lists the status in the Name column and the processes with that status in the Group column. (To change the column labels, use a hash table. For more information, see the examples in "get-help format-table -examples".)

There are a maximum of 4 services listed in the Group column for each status. To increase the number of items listed, increase the value of $FormatEnumerationLimit to 1000.

In the resulting display, the list in the Group column is now limited by the line length. In the final command in the example, use the Wrap parameter of Format-Table to display all of the processes in each Status group.

PS> $formatenumerationlimit         # Find the current value
4

PS> # List all services grouped by status
PS> 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...}
PS> # The list is truncated after 4 items.

PS> # Increase the limit to 1000.
PS> $formatenumerationlimit = 1000
PS> 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...

PS> # Add the Wrap parameter.
PS> 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 (specifically, informational messages that you have added to commands or scripts by adding the Write-Information cmdlet, and want displayed to users) for a PowerShell session. The value of the -InformationAction parameter, if used, overrides the current value of the $InformationPreference variable.

Valid values:

  • 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: No effect. The informational messages are not (Default) displayed, and the script continues without interruption.

$Log*Event

The LogEvent 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 LogEvent 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. Default = $false (not logged).

  • $LogCommandLifecycleEvent: Logs the starting and stopping of commands and command pipelines and security exceptions in command discovery. Default = $false (not logged).

  • $LogEngineHealthEvent: Logs errors and failures of sessions. Default = $true (logged).

  • $LogEngineLifecycleEvent: Logs the opening and closing of sessions. Default = $true (logged).

  • $LogProviderHealthEvent: Logs provider errors, such as read and write errors, lookup errors, and invocation errors. Default = $true (logged).

  • $LogProviderLifecycleEvent: Logs adding and removing of PowerShell providers. Default = $true (logged). (For information about PowerShell providers, type: "get-help about_provider".

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

$LogCommandLifeCycleEvent
  • or -
$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.

$MaximumAliasCount

Determines how many aliases are permitted in a PowerShell session. The default value, 4096, should be sufficient for most uses, but you can adjust it 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. This includes 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 $Error automatic variable. This variable contains an array of error record objects, one for each error. The most recent error is the first object in the array ($Error[0]).

To count the errors on your system, use the Count property of the $Error array. Type:

$Error.count

To display a specific error, use array notation to display the error. For example, to see the most recent error, type:

$Error[0]

To display the oldest retained error, type:

$Error[($Error.Count -1]

To display the properties of the ErrorRecord object, type:

$Error[0] | format-list -property * -force

In this command, the Force parameter overrides the special formatting of ErrorRecord objects and reverts to the conventional format.

To delete all errors from the error history, use the Clear method of the error array.

PS> $Error.count
17
PS> $Error.clear()
PS>
PS> $Error.count
0

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

$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, type "get-help function").

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 command 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 about the Variable provider, type "get-help variable".

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

(get-variable).count

$OFS

Output Field Separator. Specifies the character that separates the elements of an array when the array is converted to a string.

Valid values: Any string. Default: Space

By default, the $OFS variable does not exist and the output file separator is a space, but you can add this variable and set it to any string.

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.

PS> $array = 1,2,3                 # Store an array of integers.

PS> [string]$array                 # Cast the array to a string.
1 2 3                              # Spaces separate the elements

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

PS> $OFS = "+"                     # Create $OFS and assign a "+"

PS> [string]$array                 # Repeat the command
1+2+3                              # Plus signs separate the elements

To restore the default behavior, you can assign a space (" ") to the value of $OFS or delete the variable. This command deletes the variable and then verifies that the separator is a space.

PS> Remove-Variable OFS            # Delete $OFS
PS>

PS> [string]$array                 # Repeat the command
1 2 3                              # Spaces separate the elements

$OutputEncoding

Determines the character encoding method that PowerShell uses when it sends text to other applications.

For example, if an application returns Unicode strings to PowerShell, you might need to change the value to UnicodeEncoding to send the characters correctly.

Valid values: Objects derived from an Encoding class, such as ASCIIEncoding, SBCSCodePageEncoding, UTF7Encoding, UTF8Encoding, UTF32Encoding, and UnicodeEncoding.

Default: ASCIIEncoding object (System.Text.ASCIIEncoding)

EXAMPLES

This example shows how to make the FINDSTR command in Windows work in PowerShell on a computer that is localized for a language that uses Unicode characters, such as Chinese.

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

PS> $OutputEncoding.EncodingName # Find the current value US-ASCII

In this example, a FINDSTR command is used to search for two Chinese characters that are present in the Test.txt file. When this FINDSTR command is run in the Windows Command Prompt (Cmd.exe), FINDSTR finds the characters in the text file. However, when you run the same FINDSTR command in PowerShell, the characters are not found because the PowerShell sends them to FINDSTR in ASCII text, instead of in Unicode text.

PS> findstr <Unicode-characters>  # Use findstr to search.
PS>                               # None found.

To make the command work in PowerShell, set the value of $OutputEncoding to the value of the OutputEncoding property of the console, which is based on the locale selected for Windows. Because OutputEncoding is a static property of the console, use double-colons (::) in the command.

PS> $OutputEncoding = [console]::outputencoding
PS> # Set the value equal to the OutputEncoding property of the console.
PS> $OutputEncoding.EncodingName
OEM United States

As a result of this change, the FINDSTR command finds the characters.

PS> findstr <Unicode-characters>
test.txt:         <Unicode-characters>

$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 depict the status of a command.

Valid values:

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

$PSEmailServer

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

$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 (:) and the value is a custom default value that you specify.

This variable was introduced in PowerShell 3.0

For more information about this preference variable, see about_Parameters_Default_Values.

$PSModuleAutoloadingPreference

Enables and disables automatic importing of modules in the session. "All" is the default. Regardless of the value of this variable, you can use the Import-Module cmdlet to import a module.

Valid values are:

  • All: Modules are imported automatically on first-use. To import a module, get (Get-Command) or use any command in the module.
  • 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: Automatic importing of modules is disabled in the session. 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 WS-Management technology.

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 does not 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 value of this parameter 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.

This preference variable is set on the local computer, but it specifies a listener on the remote computer. If the application name that you specify does not exist on the remote computer, the command to establish the session fails.

$PSSessionConfigurationName

Specifies the default session configuration that is used for PSSessions created in the current session.

This preference variable is set on the local computer, but it specifies a session configuration that is 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 does not, the command to create a session that uses the session configuration fails.

This preference variable does not 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 (System.Management.Automation.Remoting.PSSessionObject). 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, see the help topic for the New-PSSessionOption cmdlet.

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.

For example,

$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 Windows PowerShell profile.

You can also 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.

For more information about the New-PSSessionOption cmdlet, see the help topic for New-PSSessionOption. For more information about remote commands and sessions, see about_Remote and about_PSSessions. For more information about using a profile, see about_Profiles.

$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. Typically, verbose messages describe the actions performed to execute a command.

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

You can also use the Verbose common parameter of a cmdlet to display or hide the verbose messages for a specific command. For more information, type: "get-help about_commonparameters".

Valid values:

  • 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: Does not display the verbose message. Continues executing. (Default)

EXAMPLES

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

This example shows the effect of the SilentlyContinue value, which is the default.

PS> $VerbosePreference             # Find the current value.
SilentlyContinue

PS> # Write a verbose message.
PS> Write-Verbose "Verbose message test."
PS>                   # Message is not displayed.

PS> # Use the Verbose parameter.
PS> Write-Verbose "Verbose message test." -verbose
VERBOSE: Verbose message test.

This example shows the effect of the Continue value.

PS> # Change the value to Continue.
PS> $VerbosePreference = "Continue"
PS> Write-Verbose "Verbose message test."
VERBOSE: Verbose message test.
PS> # Message is displayed.

PS> # Use the Verbose parameter with a value of $false.
PS> Write-Verbose "Verbose message test." -verbose:$false
PS> # Message is not displayed.

This example shows the effect of the Stop value.

PS> # Change the value to Stop.
PS> $VerbosePreference = "Stop"
PS> Write-Verbose "Verbose message test."
VERBOSE: Verbose message test.
Write-Verbose : Command execution stopped because the shell variable
"VerbosePreference" is set to Stop.
At line:1 char:14
+ Write-Verbose  <<<< "Verbose message test."

PS> # Use the Verbose parameter with a value of $false
PS> Write-Verbose "Verbose message test." -verbose:$false
PS>                # Message is not displayed.

This example shows the effect of the Inquire value.

PS> # Change the value to Inquire.
PS> $VerbosePreference = "Inquire"
PS> Write-Verbose "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"): y
PS>

PS> # Use the Verbose parameter.
PS> Write-Verbose "Verbose message test." -verbose:$false
PS>                #Message is not displayed.

$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.

You can also use the WarningAction common parameter of a cmdlet to determine how PowerShell responds to warnings from a particular command. For more information, type: "get-help about_commonparameters".

Valid values:

  • 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: Displays the warning message and then (Default) continues executing.
  • SilentlyContinue: Does not display the warning message. Continues executing.
EXAMPLES

These examples show the effect of the different values of $WarningPreference and the use of the WarningAction common parameter to override the preference value.

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

PS> $WarningPreference    # Find the current value.
Continue
PS> Write-Warning "This action can delete data."
WARNING: This action can delete data.

PS> # Use the WarningAction parameter to suppress the warning
PS> Write-Warning "This action can delete data." -warningaction `
 silentlycontinue

This example shows the effect of the SilentlyContinue value.

PS> # Change the value to SilentlyContinue.
PS> $WarningPreference = "SilentlyContinue"
PS> Write-Warning "This action can delete data."
PS>                        # Write a warning message.

PS> # Use the WarningAction to stop when a warning is generated.
PS> Write-Warning "This step can delete data." -warningaction stop
WARNING: This action can delete data.
Write-Warning : Command execution stopped because the shell variable
"WarningPreference" is set to Stop.
At line:1 char:14
+ Write-Warning <<<<  "This action can delete data." -warningaction stop

This example shows the effect of the Inquire value.

PS> # Change the value to Inquire.
PS> $WarningPreference = "Inquire"
PS> Write-Warning "This action can delete data."
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"): y
PS>

PS> # Use the WarningAction to continue without stopping.
PS> Write-Warning "This step can delete data." -warningaction `
 silentlycontinue

This example shows the effect of the Stop value.

PS> # Change the value to Stop.
PS> $WarningPreference = "Stop"

PS> Write-Warning "This action can delete data."
WARNING: This action can delete data.
Write-Warning : Command execution stopped because the shell variable
"WarningPreference" is set to Stop.
At line:1 char:14
+ Write-Warning  <<<< "This action can delete data."

PS> # Use the WarningAction to ask when a warning occurs.
PS> Write-Warning "This action can delete data." -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 does not execute the command.

Valid values:

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

When a cmdlet supports WhatIf, the cmdlet reports the expected effect of the command, instead of executing the command. For example, instead of deleting the test.txt file in response to a Remove-Item command, PowerShell reports what it would delete. A subsequent Get-Childitem command confirms that the file was not deleted.

PS> # What if: Performing "Remove-Item" on Target "Item: C:\test.txt"
PS> remove-item test.txt
PS> get-childitem test.txt

Directory: Microsoft.PowerShell.Core\FileSystem::C:

Mode                LastWriteTime     Length     Name
----                -------------     ------     ----
-a---         7/29/2006   7:15 PM         84     test.txt
EXAMPLES

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

This example shows the effect of the 0 (not enabled) value, which is the default.

PS> $whatifpreference
0                         # Check the current value.

PS> # Verify that the file exists.
PS> get-childitem test.txt | format-list FullName
FullName : C:\test.txt

PS> remove-item test.txt
PS>                       # Delete the file.

PS> # Verify that the file is deleted.
PS> get-childitem test.txt | format-list -property FullName

Get-ChildItem : Cannot find path 'C:\test.txt' because it does not exist.
At line:1 char:14
+ get-childitem  <<<< test.txt | format-list fullname

This example shows the effect of using the WhatIf parameter when the value of $WhatIfPreference is 0.

PS> # Verify that the file exists.
PS> get-childitem test2.txt | format-list -property FullName
FullName : C:\test2.txt

PS> # Use the WhatIf parameter
PS> remove-item test2.txt -whatif
What if: Performing operation "Remove File" on Target "C:\test2.txt".

PS> # Verify that the file was not deleted
PS> get-childitem test2.txt | format-list -property FullName
FullName : C:\test2.txt

This example shows the effect of the 1 (WhatIf enabled) value. When you use Remove-Item to delete a cmdlet, Remove-Item displays the path to the file that it would delete, but it does not delete the file.

PS> $whatifpreference = 1
PS> $whatifpreference
1                        # Change the value.

PS> # Try to delete a file.
PS> remove-item test.txt
What if: Performing operation "Remove File" on Target "C:\test.txt".

PS> # Verify that the file exists.
PS> get-childitem test.txt | format-list FullName
FullName : C:\test.txt

This example shows how to delete a file when the value of $WhatIfPreference is 1. It uses the WhatIf parameter with a value of $false.

PS> # Use the WhatIf parameter with $false.
PS> remove-item test.txt -whatif:$false

This example demonstrates that some cmdlets support WhatIf behavior and others do not. In this example, in which the value of $WhatIfPreference is 1 (enabled), a Get-Process command, which does not support WhatIf, is executed, but a Stop-Process command performs the WhatIf behavior. You can override the WhatIf behavior of the Stop-Process command by using the WhatIf parameter with a value of $false.

PS> # Change the value to 1.
PS> $whatifpreference = 1

PS> get-process winword
A Get-Process command completes.

Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName
-------  ------    -----      ----- -----   ------     -- -----------
234       8     6324      15060   154     0.36   2312 WINWORD

PS> # A Stop-Process command uses WhatIf.
PS> stop-process -name winword
What if: Performing operation "Stop-Process" on Target "WINWORD (2312)".

PS> stop-process -name winword  -whatif:$false
PS>                      # WhatIf:$false overrides the preference.

PS> # Verify that the process is stopped.
PS> get-process winword
Get-Process : Cannot find a process with the name 'winword'. Verify the
process name and call the cmdlet again.
At line:1 char:12
+ get-process  <<<< winword

SEE ALSO