PowerShell: Function Parameters

Named Parameters

Two syntax for named parameters.

simple, traditional:

function fname (param1, param2) { statements }

use the keyword param in function body:

function fname { param (param1, param2); statements }

💡 TIP: using param in body is recommended, because when param gets complex, it is less clutter.

function f ($x , $y) {
 $x + $y
}

# call
f 3 4
# 7

# call with param name
f -x 3 -y 4
# 7

# example of defining function parameter using param

function f {
 param ($x , $y)
 $x + $y
}

# call
f 3 4
# 7

# call with param name
f -x 3 -y 4
# 7

Default Value for Named Parameter

Example of adding default value: param ($x = 3 , $y = 4)

function f {
param ($x = 3 , $y = 4)
$x + $y
}

# call
f
# 7

Switch Parameter (for On or Off)

Add [switch] in front of the parameter name.

function f {
    param ([switch] $x)
    if ($x) { Write-Host  "yes" } else { Write-Host  "no" }
}

f -x
# yes

f
# no

Positional Parameters

$args[0]

$args[0], $args[1] are the parameter values.

function f {
$args[0] + $args[1]
}

f 3 4
# 7

parameter type declaration

You can declare type for parameter. For example [int] $x. 〔see Value Types〕

# declare param type
function f ([int]$x) {$x+1}

f 3
# 4