Automatic Variables

Variables that store state information for PowerShell. These variables are created and maintained by Windows PowerShell.

$$ Contains the last token in the last line received by the session.
$? Contains the execution status of the last operation. It contains TRUE if the last operation succeeded and FALSE if it failed.
$^ Contains the first token in the last line received by the session.
$_ Contains the current object in the pipeline object. You can use this variable in commands that perform an action on every object or on selected objects in a pipeline.
$Args Contains an array of the undeclared parameters and/or parameter values that are passed to a function, script, or script block. When you create a function, you can declare the parameters by using the param keyword or by adding a comma-separated list of parameters in parentheses after the function name.
$ConsoleFileName

Contains the path of the console file (.psc1) that was most recently used in the session.

This variable is populated when you start PowerShell with the PSConsoleFile parameter or when you use the Export-Console cmdlet to export snap-in names to a
console file.

When you use the Export-Console cmdlet without parameters, it automatically updates the console file that was most recently used in the session. You can use this automatic variable to determine which file will be updated.

$Error Contains an array of error objects that represent the most recent errors. The most recent error is the first error object in the array ($Error[0]).
$Event Contains a PSEventArgs object that represents the event that is being processed. This variable is populated only within the Action block of an event registration command, such as Register-ObjectEvent. The value of this variable is the same object that the Get-Event cmdlet returns. Therefore, you can use the properties of the $Event variable, such as $Event.TimeGenerated , in an Action script block.
$EventSubscriber Contains a PSEventSubscriber object that represents the event subscriber of the event that is being processed. This variable is populated only within the Action block of an event registration command. The value of this variable is the same object that the Get-EventSubscriber cmdlet returns.
$ExecutionContext Contains an EngineIntrinsics object that represents the execution context of the Windows PowerShell host. You can use this variable to find the execution objects that are available to cmdlets. $False Contains FALSE. You can use this variable to represent FALSE in commands and scripts instead of using the string "false". The string can be interpreted as TRUE if it is converted to a non-empty string or to a non-zero integer.
$ForEach Contains the enumerator of a ForEach-Object loop. You can use the properties and methods of enumerators on the value of the $ForEach variable. This variable exists only while the For loop is running. It is deleted when the loop is completed.
$Home Contains the full path of the user's home directory. This variable is the equivalent of the %homedrive%%homepath% environment variables, typically C:\Documents and Settings\<user>
$Host Contains an object that represents the current host application for Windows PowerShell. You can use this variable to represent the current host in commands or to display or change the properties of the host, such as $Host.version or $Host.CurrentCulture, or $host.ui.rawui.setbackgroundcolor("Red").
$Input An enumerator that contains the input that is passed to a function. The $Input variable is case-sensitive and is available only in functions and in script blocks. (Script blocks are essentially unnamed functions.) In the Process block of a function, the $Input variable contains the object that is currently in the pipeline. When the Process block is completed, the value of $Input is NULL. If the function does not have a Process block, the value of $Input is available to the End block, and it contains all the input to the function.
$LastExitCode Contains the exit code of the last Windows-based program that was run.
$Matches The $Matches variable works with the -match and -not match operators. When you submit scalar input to the -match or -notmatch operator, and either one detects a match, they return a Boolean value and populate the $Matches automatic variable with a hash table of any string values that were matched. For more information about the -match operator, see about_comparison_operators.
$MyInvocation

Contains an object with information about the current command, such as a script, function, or script block. You can use the information in the object, such as the path and file name of the script ($myinvocation.mycommand.path) or the name of a function ($myinvocation.mycommand.name) to identify the current command. See also $PSScriptRoot

$NestedPromptLevel Contains the current prompt level. A value of 0 indicates the original prompt level. The value is incremented when you enter a nested level and decremented when you exit it. For example, Windows PowerShell presents a nested command prompt when you use the $Host.EnterNestedPrompt method. Windows PowerShell also presents a nested command prompt when you reach a breakpoint in the Windows PowerShell debugger. When you enter a nested prompt, Windows PowerShell pauses the current command, saves the execution context, and increments the value of the $NestedPromptLevel variable. To create additional nested command prompts (up to 128 levels) or to return to the original command prompt, complete the command, or type "exit". The $NestedPromptLevel variable helps you track the prompt level. You can create an alternative Windows PowerShell command prompt that includes this value so that it is always visible.
$NULL Contains a NULL or empty value. A scalar value that contains nothing.
$PID Contains the process identifier (PID) of the process that is hosting the current Windows PowerShell session.
$Profile Contains the full path of the Windows PowerShell profile for the current user and the current host application. You can use this variable to represent the profile in commands. For example, you can use it in a command to determine whether a profile has been created: test-path $profile Or, you can use it in a command to create a profile: new-item -type file -path $pshome -force You can also use it in a command to open the profile in Notepad: notepad $profile
$PSBoundParameters Contains a dictionary of the active parameters and their current values. This variable has a value only in a scope where parameters are declared, such as a script or function. You can use it to display or change the current values of parameters or to pass parameter values to another script or function. For example: function test { param($a, $b) # Display the parameters in dictionary format. $psboundparameters # Call the Test1 function with $a and $b. test1 @psboundparameters } $PsCmdlet Contains an object that represents the cmdlet or advanced function that is being run. You can use the properties and methods of the object in your cmdlet or function code to respond to the conditions of use. For example, the ParameterSetName property contains the name of the parameter set that is being used, and the ShouldProcess method adds the WhatIf and Confirm parameters to the cmdlet dynamically. For more information about the $PSCmdlet automatic variable, see about_Functions_Advanced.
$PsCulture Contains the name of the culture currently in use in the operating system. The culture determines the display format of items such as numbers, currrency, and dates. This is the value of the System.Globalization.CultureInfo.CurrentCulture.Name property of the system. To get the System.Globalization.CultureInfo object for the system, use the Get-Culture cmdlet.
$PSDebugContext While debugging, this variable contains information about the debugging environment. Otherwise, it contains a NULL value. As a result, you can use it to indicate whether the debugger has control. When populated, it contains a PsDebugContext object that has Breakpoints and InvocationInfo properties. The InvocationInfo property has several useful properties, including the Location property. The Location property indicates the path of the script that is being debugged.
$PsHome Contains the full path of the installation directory for Windows PowerShell, typically, %windir%\System32\WindowsPowerShell\v1.0. You can use this variable in the paths of Windows PowerShell files. For example, the following command searches the conceptual Help topics for the word "variable": select-string -pattern variable -path $pshome\*.txt
$PSScriptRoot

Contains the directory from which the script module is being executed.

This variable allows scripts to use the module path to access other resources.
In PowerShell 3.0+ this is available everywhere, not just in modules.

$PsUICulture Contains the name of the user interface (UI) culture that is currently in use in the operating system. The UI culture determines which text strings are used for user interface elements, such as menus and messages. This is the value of the System.Globalization.CultureInfo.CurrentUICulture.Name property of the system. To get the System.Globalization.CultureInfo object for the system, use Get-UICulture.
$PsVersionTable

Contains a read-only hash table that displays details about the version of Windows PowerShell that is running in the current session. The table includes the following items:

  CLRVersion:            The version of the common language runtime (CLR)
  BuildVersion:          The build number of the current version
  PSVersion:             The Windows PowerShell version number
  WSManStackVersion:     The version number of the WS-Management stack
  PSCompatibleVersions:  Versions of Windows PowerShell that are
                                   compatible with the current version
  SerializationVersion   The version of the serialization method
  PSRemotingProtocolVersion
                         The version of the Windows PowerShell remote
                         management protocol
$Pwd Contains a path object that represents the full path of the current directory.
$Sender Contains the object that generated this event. This variable is populated only within the Action block of an event registration command. The value of this variable can also be found in the Sender property of the PSEventArgs (System.Management.Automation.PSEventArgs) object that Get-Event returns.
$ShellID Contains the identifier of the current shell.
$SourceArgs Contains objects that represent the event arguments of the event that is being processed. This variable is populated only within the Action block of an event registration command. The value of this variable can also be found in the SourceArgs property of the PSEventArgs (System.Management.Automation.PSEventArgs) object that Get-Event returns.
$SourceEventArgs Contains an object that represents the first event argument that derives from EventArgs of the event that is being processed. This variable is populated only within the Action block of an event registration command. The value of this variable can also be found in the SourceArgs property of the PSEventArgs (System.Management.Automation.PSEventArgs) object that Get-Event returns.
$This In a script block that defines a script property or script method, the $This variable refers to the object that is being extended.
$True Contains TRUE. You can use this variable to represent TRUE in commands and scripts.

“When he ran from a cop his transitions from accelerating walk to easy jog trot to brisk canter to headlong gallop to flogged-piston sprint were as distinct and as soberly in order as an automatic gearshift” ~ James Agee

Related:

Get-Variable - Get a PowerShell variable
Hash Tables
Preference Variables
Variables - Create & read variables


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