Problem
You want to access the arguments provided to a script, function, or script block.
Solution
To access arguments by name, use a param statement:
param($firstNamedArgument, [int] $secondNamedArgument = 0)
"First named argument is: $firstNamedArgument" "Second named argument is: $secondNamedArgument"
To access unnamed arguments by position, use the $args array:
"First positional argument is: " + $args[0] "Second positional argument is: " + $args[1]
You can use these techniques in exactly the same way with scripts, functions, and script blocks, as illustrated by Example 106.
Example 106. Working with arguments in scripts, functions, and script blocks
############################################################################## ## GetArguments.ps1 ## ## Use commandline arguments ############################################################################## param($firstNamedArgument, [int] $secondNamedArgument = 0)
## Display the arguments by name "First named argument is: $firstNamedArgument" "Second named argument is: $secondNamedArgument"
function GetArgumentsFunction { ## We could use a param statement here, as well ## param($firstNamedArgument, [int] $secondNamedArgument = 0)
## Display the arguments by position "First positional function argument is: " + $args[0] "Second positional function argument is: " + $args[1] }
GetArgumentsFunction One Two
$scriptBlock = { param($firstNamedArgument, [int] $secondNamedArgument = 0)
## We could use $args here, as well "First named scriptblock argument is: $firstNamedArgument" "Second named scriptblock argument is: $secondNamedArgument"
}
& $scriptBlock First One Second 4.5
Example 106 produces the following output:
PS >GetArguments First 2 First named argument is: First Second named argument is: 2 First positional function argument is: One Second positional function argument is: Two First named scriptblock argument is: One Second named scriptblock argument is: 4
Discussion
Although PowerShell supports both the param keyword and the $args array, you will most commonly want to use the param keyword to define and access script, function, and script block parameters.
In most languages, the most common reason to access parameters through an $argsstyle array is to determine the name of the currently running script. For information about how to do this in PowerShell.
When you use the param keyword to define your parameters, PowerShell provides your script or function with many useful features that allow users to work with your script much like they work with cmdlets:
- Users need only to specify enough of the parameter name to disambiguate it from other parameters.
- Users can understand the meaning of your parameters much more clearly.
- You can specify the type of your parameters, which PowerShell uses to convert input if required.
- You can specify default values for your parameters.
The $args array is sometimes helpful, however, as a way to deal with all arguments at once. For example:
function Reverse
{ $argsEnd = $args.Length 1 $args[$argsEnd..0]
}
produces
PS >Reverse 1 2 3 4 4 3 2 1
