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About Script Blocks

JuanPablo Jofre|Last Updated: 11/17/2016
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2 Contributors

about_Script_Blocks

SHORT DESCRIPTION

Defines what a script block is and explains how to use script blocks in the Windows PowerShell programming language.

LONG DESCRIPTION

In the Windows PowerShell programming language, a script block is a collection of statements or expressions that can be used as a single unit. A script block can accept arguments and return values.

Syntactically, a script block is a statement list in braces, as shown in the following syntax:

{}

A script block returns the output of all the commands in the script block, either as a single object or as an array.

Like functions, a script block can include parameters. Use the Param keyword to assign named parameters, as shown in the following syntax:

{ param ([type]$parameter1 [,[type]$parameter2]) }

In a script block, unlike a function, you cannot specify parameters outside the braces.

Like functions, script blocks can include the DynamicParam, Begin, Process, and End keywords. For more information, see about_Functions and about_Functions_Advanced.

Using Script Blocks

A script block is an instance of a Microsoft .NET Framework type (System.Management.Automation.ScriptBlock). Commands can have script block parameter values. For example, the Invoke-Command cmdlet has a ScriptBlock parameter that takes a script block value, as shown in this example:

C:\PS> invoke-command -scriptblock { get-process } Handles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id ProcessName


999 28 39100 45020 262 15.88 1844 communicator 721 28 32696 36536 222 20.84 4028 explorer

. . .

The script block that is used as a value can be more complicated, as shown in the following example:

C:\PS> invoke-command -scriptblock { param ($uu = "Parameter"); "$uu assigned." } Parameter assigned.

The script block in the preceding example uses the Param keyword to create a parameter that has a default value. The following example uses the Args parameter of the Invoke-Command cmdlet to assign a different value to the parameter:

C:\PS> invoke-command -scriptblock {param ($uu = "Parameter"); "$uu assigned."} -args "Other value" Other value assigned.

You can assign a script block to a variable, as shown in the following example:

C:\PS> $a = {param ($uu = "Parameter"); "$uu assigned."}

You can use the variable with a cmdlet such as Invoke-Command, as shown in the following example:

C:\PS> invoke-command -scriptblock $a -args "Other value" Other value assigned.

You can run a script block that is assigned to a variable by using the call operator (&), as shown in the following example:

C:\PS> &$a Parameter assigned.

You can also provide a parameter to the script block, as shown in the following example:

C:\PS> &$a "Other value" Other value assigned.

If you want to assign the value that is created by a script block to a variable, use the call operator to run the script block directly, as shown in the following example:

C:\PS> $a = &{param ($uu = "Parameter"); "$uu assigned."} C:\PS> $a Parameter assigned.

For more information about the call operator, see about_Operators.

SEE ALSO

about_Functions about_Functions_Advanced about_Operators

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