Windows PowerShell Pocket Reference

Chapter 4. PowerShell Automatic Variables

PowerShell defines and populates several variables automatically. These variables let you access information about the execution environment, PowerShell preferences, and more.

Table 4-1 provides a listing of these automatic variables and their meanings.

Table 4-1. Windows PowerShell automatic variables: Variables automatically used and set by Windows PowerShell

Variable	Meaning
$$	Last token of the last line received by the shell.
$?	Success/fail status of the last operation.
$^	First token of the last line received by the shell.
$_	Current pipeline object in a pipelined script block.
$args	Array of parameters passed to the script, function, or script block.
$confirmPreference	Preference that controls the level of impact that operations may have before requesting confirmation. Supports the values none, low, medium, high. A value of none disables confirmation messages.
$consoleFilename	Filename of the PowerShell console file that configured this session, if one was used.
$currentlyExecutingCommand	Currently executing command, when in a suspended prompt.
$debugPreference	Preference that controls how PowerShell should handle debug output written by a script or cmdlet. Supports the values SilentlyContinue, Continue, Inquire, and Stop.
$error	Array that holds the terminating and nonterminating errors generated in the shell.
$errorActionPreference	Preference that controls how PowerShell should handle error output written by a script or cmdlet. Supports the values SilentlyContinue, Continue, Inquire, and Stop.
$errorView	Preference that controls how PowerShell should output errors in the shell. Supports the values of Normal and CategoryView (a more succinct and categorical view of the error).
$executionContext	Means by which scripts can access the APIs typically used by cmdlets and providers.
$false	Variable that represents the Boolean value False.
$foreach	Enumerator within a foreach loop.
$formatEnumerationLimit	Limit on how deep into an object the formatting and output facilities travel before outputting an object.
$home	User’s home directory.
$host	Means by which scripts can access the APIs and implementation details of the current host and user interface.
$input	Current input pipeline in a pipelined script block.
$lastExitCode	Exit code of the last command. Can be explicitly set by scripts, and is automatically set when calling native executables.
$logEngineHealthEvent	Preference that tells PowerShell to log engine health events, such as errors and exceptions. Supports the values $true and $false.
$logEngineLifecycleEvent	Preference that tells PowerShell to log engine lifecycle events, such as Start and Stop. Supports the values $true and $false.
$logCommandHealthEvent	Preference that tells PowerShell to log command health events, such as errors and exceptions. Supports the values $true and $false.
$logCommandLifecycleEvent	Preference that tells PowerShell to log command lifecycle events, such as Start and Stop. Supports the values $true and $false.
$logProviderHealthEvent	Preference that tells PowerShell to log provider health events, such as errors and exceptions. Supports the values $true and $false.
$logProviderLifecycleEvent	Preference that tells PowerShell to log provider lifecycle events, such as Start and Stop. Supports the values $true and $false.
$matches	Results of the last successful regular expression match (through the –match operator).
$maximumAliasCount	Limit on how many aliases may be defined.
$maximumDriveCount	Limit on how many drives may be defined. Does not include default system drives.
$maximumErrorCount	Limit on how many errors PowerShell retains in the $error collection.
$maximumFunctionCount	Limit on how many functions may be defined.
$maximumHistoryCount	Limit on how many history items are retained.
$maximumVariableCount	Limit on how many variables may be defined.
$myInvocation	Information about the context under which the script, function, or script block was run, including detailed information about the command (MyCommand) and the script that defines it (ScriptName).
$nestedPromptLevel	Nesting level of the current prompt. Incremented by operations that enter a nested prompt (such as $host.EnterNestedPrompt( )) and decremented by the exit statement.
$null	Variable that represents the concept of Null.
$ofs	Output field separator. Placed between elements when PowerShell outputs a list as a string.
$outputEncoding	Character encoding used when sending pipeline data to external processes.
$pid	Process ID of the current PowerShell instance.
$profile	Location and filename of the PowerShell profile for this host.
$progressPreference	Preference that controls how PowerShell should handle progress output written by a script or cmdlet. Supports the values SilentlyContinue, Continue, Inquire, and Stop.
$psHome	Installation location of PowerShell.
$pwd	Current working directory.
$shellId	Shell identifier of this host.
$stackTrace	Detailed stack trace information of the last error.
$this	Reference to the current object in ScriptMethods and ScriptProperties.
$transcript	Filename used by the Start-Transcript cmdlet.
$true	Variable that represents the Boolean value True.
$verboseHelpErrors	Preference that tells PowerShell to output detailed error information when parsing malformed help files. Supports the values $true and $false.
$verbosePreference	Preference that controls how PowerShell should handle verbose output written by a script or cmdlet. Supports the values SilentlyContinue, Continue, Inquire, and Stop.
$warningPreference	Preference that controls how PowerShell should handle warning output written by a script or cmdlet. Supports the values SilentlyContinue, Continue, Inquire, and Stop.
$whatifPreference	Preference that controls how PowerShell should handle confirmation requests called by a script or cmdlet. Supports the values SilentlyContinue, Continue, Inquire, and Stop.