Variables that customize the behavior of Windows PowerShell (about_preference_variables)

   
# TOPIC
Preference Variables

# SHORT DESCRIPTION
Variables that customize the behavior of Windows PowerShell

# LONG DESCRIPTION
Windows 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 Windows 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
$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 64
$MaximumVariableCount 4096
$OFS (Space character (" "))
$OutputEncoding ASCIIEncoding object
$ProgressPreference Continue
$PSEmailServer (None)
$PSSessionApplicationName WSMAN
$PSSessionConfigurationName http://schemas.microsoft.com/powershell/microsoft.powershell
$PSSessionOption (See below)
$VerbosePreference SilentlyContinue
$WarningPreference Continue
$WhatIfPreference 0

Windows Powershell also includes the following environment variables that
store user preferences. For more information about the environment variables,
see about_environment_variables.

Variable
--------
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, Windows 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
Windows PowerShell window. To make them effective in all Windows
PowerShell windows, add them to your Windows 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 Windows 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 which cmdlet actions automatically request confirmation
from the user before they are performed.

When the $ConfirmPreference value (High, Medium, Low, None) is
greater than or equal to the risk of the cmdlet action (High, Medium,
Low, None), Windows PowerShell automatically requests confirmation
from the user before performing the action.

You can use the Confirm parameter of a cmdlet to override the preference
for a specific command.

Valid values:
None: No cmdlet actions are automatically confirmed.
Users must use the Confirm parameter to request
confirmation of specific commands.

Low: Cmdlet actions with a low, medium, or high risk are
automatically confirmed. To suppress confirmation
of a specific command, use -Confirm:$false.

Medium: Cmdlet actions with a medium or high risk are
automatically confirmed. To enable confirmation of
a specific command, use -confirm. To suppress
confirmation of a specific command, use
-confirm:$false.

High: Cmdlet actions with a high risk are automatically
(default) confirmed. To enable confirmation of a specific
command, use -confirm. To suppress confirmation for a
specific command, use -confirm:$false.

DETAILED EXPLANATION
When a cmdlet action significantly affects the system, such as by
deleting data or by using a significant amount of system resources,
Windows PowerShell can automatically prompt you for confirmation
before performing the action.

For example,

PS> remove-item pref2.txt

Confirm
Are you sure you want to perform this action?
Performing operation "Remove File" on Target "C:\pref2.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 part of the cmdlet known as its
"ConfirmImpact". You cannot change it.

Cmdlet that might pose a risk to the system have a Confirm parameter
that you can use to request or suppress confirmation for a
specific command.

Because most cmdlets use the default risk value 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 cmdlet
actions. Since most actions are of medium risk, they are not
automatically confirmed, although you can use the Confirm
parameter of the cmdlet to request confirmation of a specific
command.

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

PS> remove-item temp1.txt #Delete a file
PS> #Deleted without confirmation
PS> remove-item temp2.txt -confirm #Use the Confirm parameter

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"):

This example shows the effect of changing the value of
$ConfirmPrefernce to Medium. Because most cmdlet actions are
medium-risk, they are automatically confirmed, and you have to use
the Confirm parameter with a value of $false to suppress the
confirmation prompt for a specific command.

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 Confirm parameter
to suppress confirmation
PS>

$DebugPreference
------------------
Determines how Windows 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.

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
SilentlyContinue $DebugPreference

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

PS> write-debug "Hello, World" -Debug # Use the Debug parameter
DEBUG: Hello, World # The debug message is
is requested. displayed and confirmation
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 # The debug message is displayed
PS> and processing continues.

PS> write-debug "Hello, World" -Debug:$false
# Use the Debug parameter with
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 "DebugPreference" is
set to Stop.
At line:1 char:12
+ write-debug <<<< "Hello, World"

PS> write-debug "Hello, World" -Debug:$false
# Use the Debug parameter with
$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> write-debug "Hello, World" -Debug:$false
# Use the Debug parameter with
$false
PS> # The debug message is not
displayed and processing
continues without interruption.

$ErrorActionPreference
----------------------
Determines how Windows 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. For more
information, type: "get-help about_commonparameters".

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
executing.

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

Neither $ErrorActionPreference nor the ErrorAction common parameter
affect how Windows PowerShell responds to terminating errors (those
that stop cmdlet processing).

For more information about the ErrorAction common parameter, type
"get-help 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> $erroractionpreference
Continue # Display the value of the preference.

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

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

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

This example shows the effect of the SilentlyContinue value.

PS> $ErrorActionPreference = "SilentlyContinue"
# Change the value of the preference.
PS> write-error "Hello, World"
# Generate an error message.
PS>
# Error message is suppressed.
PS> write-error "Hello, World" -erroraction:continue
# Use the ErrorAction parameter with a
value of "Continue".
write-error "Hello, World" -erroraction:continue : Hello, World
# The error message is displayed and
execution continues.

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> $ErrorActionPreference = "Continue"
# Change the value to 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> get-childitem -path nofile.txt -erroraction SilentlyContinue
# Use the ErrorAction parameter
PS>
# Error message is suppressed.

PS> $ErrorActionPreference = "Inquire"
# Change the value to 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> $ErrorActionPreference = "Continue"
# Change the value to Continue.
PS> Get-Childitem nofile.txt -erroraction "Inquire"
# 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 Windows
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 Windows 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], ItemNotFoundException

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(String path,
Boolean recurse, 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

$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, Windows 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> get-service | group-object -property status
# List all services grouped by
status

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

# The list is truncated after
4 items.

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

PS> get-service | group-object -property status
# Repeat the command.

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

PS> get-service | group-object -property status | format-table -wrap
# Add the Wrap parameter.

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, RSVP, SCardSvr, SwPrv, SysmonLog, TlntSvr, upnphost,
UPS, VSS, WmdmPmSN, Wmi, WmiApSrv, xmlprov}

$Log*Event
----------
The Log*Event preference variables determine which types of events
are written to the Windows 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. 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 Windows PowerShell providers.
Default = $true (logged). (For information about Windows 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 Windows PowerShell
console. To apply the configuration to all consoles, save the variable settings
in your Windows PowerShell profile.

$MaximumAliasCount
------------------
Determines how many aliases are permitted in a Windows 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 Windows PowerShell drives are permitted in a
given session. This includes file system drives and data stores that
are exposed by Windows 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 Windows PowerShell
Function: drive that is exposed by the Windows 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: 64

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, type:
"get-help 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 Windows PowerShell Variable: drive and the
Windows 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 used by Windows PowerShell
when it sends text to other applications. For example, if an
application returns Unicode strings to Windows PowerShell, you might
need to change the value to 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 Windows 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 Windows PowerShell, the characters are not found
because the Windows 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 Windows 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
# Find the resulting value.

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

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

# Use findstr to search. It find the
characters in the text file.

$ProgressPreference
-------------------
Determines how Windows 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.

$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.

You can also set custom options for a particular remote session by
using the SessionOption parameter in cmdlets that create a session,
such as New-PSSession, Enter-PSSession, and Invoke-Command. The
SessionOption parameter value takes precedence over the system defaults
and the defaults that are set in this variable.

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.

To create the $PSSessionOption preference variable, use the
New-PSSessionOption cmdlet. Save the output in a variable called
$PSSessionOption.

For example,

$PSSessionOption = New-PSSessionOption -NoCompression

To use the $PSSessionOption preference variable in every
Windows PowerShell session, add a New-PSSessionOption command
that creates the $PSSessionOption variable to your Windows
PowerShell profile.

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

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

This example shows the effect of the Continue value.

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

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

This example shows the effect of the Stop value.

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

This example shows the effect of the Inquire value.

PS> $VerbosePreference = "Inquire"
# Change the value to Inquire.
PS> Write-Verbose "Verbose message test."
VERBOSE: Verbose message test.
# Write a verbose message.
Confirm
Continue with this operation?
[Y] Yes [A] Yes to All [H] Halt Command [S] Suspend [?] Help (default is "Y"): y
PS>

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

$WarningPreference
------------------
Determines how Windows 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 Windows 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

# Write a warning message.
PS> Write-Warning "This action can delete data."
WARNING: This action can delete data.

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

This example shows the effect of the SilentlyContinue value.

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

PS> Write-Warning "This action can delete data."
PS> # Write a warning message.

PS> Write-Warning "This action can delete data." -warningaction stop
# Use the WarningAction parameter to stop
# processing when this command generates a
# warning.
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> $WarningPreference = "Inquire"
# Change the value to Inquire.
PS> Write-Warning "This action can delete data."
# Write a warning message.
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> Write-Warning "This action can delete data." -warningaction silentlycontinue
PS> # Use the WarningAction parameter to change the
# response to a warning for the current command.

This example shows the effect of the Stop value.

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

PS> Write-Warning "This action can delete data."
# Write a warning message.
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> 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"):
# Use the WarningAction parameter to change the
# response to a warning for the current command.

$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).

DETAILED EXPLANATION

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, Windows PowerShell reports what it would
delete. A subsequent Get-Childitem command confirms that the file
was not deleted.

PS> remove-item test.txt
What if: Performing operation "Remove-Item" on Target "Item:
C:\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> get-childitem test.txt | format-list FullName
FullName : C:\test.txt
# Verify that the file exists.

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

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

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

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

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

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

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

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> remove-item test.txt -whatif:$false
# Use the WhatIf parameter with $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> $whatifpreference = 1
# Change the value to 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> stop-process -name winword
What if: Performing operation "Stop-Process" on Target "WINWORD (2312)".
# A Stop-Process command uses WhatIf.

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

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
# Verify that the process is stopped.

SEE ALSO
about_Automatic_Variables
about_CommonParameters
about_Environment_Variables
about_Profiles
about_Remote
about_Scopes
about_Variables

C:\Windows>powershell get-help about_profiles -full

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