TOPIC about_Parameters SHORT DESCRIPTION Describes how to work with cmdlet parameters in Windows PowerShell. LONG DESCRIPTION Most Windows PowerShell cmdlets and functions rely on parameters to allow users to select options or provide input. The parameters follow the cmdlet or function name and typically have the following form: -<parameter_name> <parameter_value> The name of the parameter is preceded by a hyphen (-), which signals to Windows PowerShell that the word following the hyphen is a parameter and not a value being passed to the cmdlet or function. Not all parameters require a value, and not all parameter names must be specified. In some cases, the parameter name is implied and does not need to be included in the command. The type of parameters and the requirements for those parameters vary by cmdlet and by function from cmdlet to cmdlet. To find information about the parameters of a cmdlet, use the Get-Help cmdlet. For example, to find information about the parameters of the Get-ChildItem cmdlet, type: get-help get-childitem To find information about the parameters of a function, review the parameter definitions. Parameters are defined either after the function name or inside the body of the function, using the Param keyword. For more information, see about_Functions. Some functions also contain comment-based Help about parameters. Use the Get-Help cmdlet with these functions. For more information, see the help topic for Get-Help and about_Comment_Based_Help. The Get-Help Cmdlet returns various details about the cmdlet or function, including a description of the cmdlet or function, the command syntax, information about the parameters, and examples showing how to use the cmdlet or function. You can also use the Parameter parameter of the Get-Help cmdlet or function to find information about a particular parameter. Or, you can use the wildcard character (*) with the Parameter parameter to find information about all the parameters of the cmdlet or function. For example, the following command gets information about all the parameters of the Get-Member cmdlet or function: get-help get-member -parameter * This information includes the details you need to know to use the parameter. For example, the Help topic for the Get-ChildItem cmdlet includes the following details about its Path parameter: -path <string[]> Specifies a path of one or more locations. Wildcard characters are permitted. The default location is the current directory (.). Required? false Position? 1 Default value Current directory Accept pipeline input? true (ByValue, ByPropertyName) Accept wildcard characters? true The parameter information includes the parameter syntax, a description of the parameter, and the parameter attributes. The following sections describe the parameter attributes. Parameter Required? This setting indicates whether the parameter is mandatory, that is, whether all commands that use this cmdlet must include this parameter. When the value is "True" and the parameter is missing from the command, Windows PowerShell prompts you for a value for the parameter. Parameter Position? This setting indicates whether you can supply a parameter's value without preceding it with the parameter name. If set to "0" or "named," a parameter name is required. This type of parameter is referred to as a named parameter. A named parameter can be listed in any position after the cmdlet name. If the "Parameter position?" setting is set to an integer other than 0, the parameter name is not required. This type of parameter is referred to as a positional parameter, and the number indicates the position in which the parameter must appear in relation to other positional parameters. If you include the parameter name for a positional parameter, the parameter can be listed in any position after the cmdlet name. For example, the Get-ChildItem cmdlet has Path and Exclude parameters. The "Parameter position?" setting for Path is 1, which means that it is a positional parameter. The "Parameter position?" setting for Exclude is 0, which means that it is a named parameter. This means that Path does not require the parameter name, but its parameter value must be the first or only unnamed parameter value in the command. However, because the Exclude parameter is a named parameter, you can place it in any position in the command. As a result of the "Parameter position?" settings for these two parameters, you can use any of the following commands: Get-ChildItem -path c:\techdocs -exclude *.ppt Get-ChildItem c:\techdocs -exclude *.ppt Get-ChildItem -exclude *.ppt -path c:\techdocs Get-ChildItem -exclude *.ppt c:\techdocs If you were to include another positional parameter without including the parameter name, that parameter would have to be placed in the order specified by the "Parameter position?" setting. Parameter Type This setting specifies the Microsoft .NET Framework type of the parameter value. For example, if the type is Int32, the parameter value must be an integer. If the type is string, the parameter value must be a character string. If the string contains spaces, the value must be enclosed in quotation marks, or the spaces must be preceded by the escape character (`). Default Value This setting specifies the value that the parameter will assume if no other value is provided. For example, the default value of the Path parameter is often the current directory. Required parameters never have a default value. For many optional parameters, there is no default because the parameter has no effect if it is not used. Accepts Multiple Values? This setting indicates whether a parameter accepts multiple parameter values. When a parameter accepts multiple values, you can type a comma-separated list as the value of the parameter in the command, or save a comma-separated list (an array) in a variable, and then specify the variable as the parameter value. For example, the ServiceName parameter of the Get-Service cmdlet accepts multiple values. The following commands are both valid: get-service -servicename winrm, netlogon $s = "winrm", "netlogon" get-service -servicename $s Accepts Pipeline Input? This setting indicates whether you can use the pipeline operator (|) to send a value to the parameter. Value Description ----- ----------- False Indicates that you cannot pipe a value to the parameter. True (by Value) Indicates that you can pipe any value to the parameter, just so the value has the .NET Framework type specified for the parameter or the value can be converted to the specified .NET Framework type. When a parameter is "True (by Value)", Windows PowerShell tries to associate any piped values with that parameter before it tries other methods to interpret the command. True (by Property Name) Indicates that you can pipe a value to the parameter, but the .NET Framework type of the parameter must include a property with the same name as the parameter. For example, you can pipe a value to a Name parameter only when the value has a property called "Name". Accepts Wildcard Characters? This setting indicates whether the parameter's value can contain wildcard characters so that the parameter value can be matched to more than one existing item in the target container. Common Parameters Common parameters are parameters that you can use with any cmdlet. For more information, about common parameters, type: help about_commonparameters SEE ALSO about_Command_syntax about_Comment_Based_Help about_Functions_Advanced about_Pipelines about_Wildcards