Parameters: general guide
In powershell, parameters -- you know, arguments -- can be written in a lot of ways.
Even a script that declares no parameters can access the parameters that are handed to it.
As can a function, a named cmdLet, etc.
You can declare parameter names without specifying a type, e.g.
function New-Satellite ($satelliteName, $weightInGrams) {
write-host "The $satelliteName will weigh $weightInGrams" -f Yellow;
}
...and a trap for young players, having just written such a function...
You call it WITHOUT parentheses.
You call it like this:
New-Satellite "The Nazgul Banana" 500
and NOT like this:
New-Satellite ("The Nazgul Banana", 500) # NO! Not like this!
...as that would be interpreted as you sending a single parameter, an array with two values
("The Nazgul Banana", 500).GetType()
IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True Object[] System.Array
Hence $SatelliteName would be an array of objects.
Apart from remembering the "no brackets" syntax -- you also need to learn how to give types to your parameters, and so much more.
param()
Function Invoke-Clippy{
param(
$text="Hi! I am Clippy, your office assistant. Would you like some assistance today?"
)
write-host $text -foregroundColor yellow;
}
[string]
param (
[string]$text
)
[Parameter()]
param (
[Parameter(Mandatory)]
$ApiKey
)
[ValidateNotNullOrEmpty()]
param (
[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[string]$ApiKey
)
todo: ValueFromPipeline
[CmdletBinding()]
[ValueFromPipelineByPropertyName()]
function kvi {
# AAA reads stream. you give it an object. it will iterate it and return an object which is the keys.
[CmdletBinding()]
Param(
[Parameter(ValueFromPipelineByPropertyName)]$Keys,
[Parameter(ValueFromPipelineByPropertyName)]$Value
)
param (
[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[string]$ApiKey
)
[ParameterSetName]
[Parameter(Mandatory, ParameterSetName = 'ById')]
Another example
[Parameter(Mandatory, ParameterSetName = 'ById')]
[CmdletBinding()]
Param(
[Parameter(Mandatory, ParameterSetName = 'ById')]
[ValidateNotNullOrEmpty()]
[Alias('BaseName', 'BaseId')]
[string]$BaseIdentity,
[Parameter(Mandatory, ParameterSetName = 'ById')]
[ValidateNotNullOrEmpty()]
[string]$Table,
[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[hashtable]$Fields,
[switch]$PassThru
)
PSAvoidUsingPositionalParameters
- PSAvoidUsingPositionalParameters
ValueFromRemainingArguments
- ValueFromRemainingArguments
Passthrough
- Passthrough
Source(s)
- looking through my own code and documenting things i've learned once and forgotten since, in hope i will remember them again.
- https://adamtheautomator.com/powershell-parameter/#Creating_a_Simple_PowerShell_Parameter