Windows 7 / Getting Started

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Parentheses, Brackets, and Braces

PowerShell commands can include parentheses (( )), brackets ([ ]), and braces ({ }). Braces are also referred to as "curly brackets" and even "funky brackets" by some. Each is interpreted differently within PowerShell.

Parentheses ( ) Parentheses are commonly used to provide arguments. For example, when a script needs to accept a parameter, you can use Param($input). Here the $input is identifi ed as an argument for the Param command.

Note The terms parameter and argument are often used interchangeably On one level, they are the same thing; but there is a subtle difference between the two A parameter is provided as input to a piece of code, and an argument is what is provided The value is the same but the perspective is different A parameter is passed in, and the value of this parameter is used as an argument within the code.

Brackets [ ] Brackets are used for various purposes. You'll see them used when accessing arrays, when using -like comparisons, and with some parameters. As an example, the following command uses them to indicate the output should include only names that start with a letter:

Get-wmiObject Win32_ComputerSystem | Format-List [a-z]*

Braces { } Braces are used to enclose a portion of code within a statement that is interpreted as a block of code. You'll see them in condition statements (like ForEach seen later in the tutorial). The following example shows how braces are used to separate the block in the Where clause in a single line of code:

Get-service | Select * | Where {$_.name -eq $Name}

The point here is not that you need to memorize when these characters need to be used. Instead, the goal is to let you know that all three could be used and, when you're executing code and writing scripts, to recognize each. If you replace curly braces with parentheses when you type in your own code, you'll fi nd things simply don't work.