How to run a script with optional parameters?

Question

I would like to run a script which creates a VM in Azure.

These are the mandatory parameters:

$cred = Get-Credential -Message "Enter a username and password for the virtual machine."
$RG = 'AZ-PS-RG'
$VM_NAME = 'AZ-PS-VM'
$location = 'francecentral'
$image = 'UbuntuLTS'
$size = 'Standard_D2s_v3'
$vnetName='myVNet'
$SubnetName = 'mySubnet-ps'

I would also like to provide two optional parameters for PublicIpAddressName and DomainNameLabel:

$dnsName=''
$reservedIP= ''

The idea is that the script should check if those parameters are empty or not. If they are empty then simply create a VM with only mandatory parameters:

$vmParams = @{
  ResourceGroupName = $RG
  Name = $VM_NAME
  Location = $location
  ImageName = $image
  Credential = $cred
  VirtualNetworkName = $vnetName
  SubnetName = $SubnetName
  Size = $size
  # these two I would like to run only if they are provided
  PublicIpAddressName = $reservedIP
  DomainNameLabel = $dnsName

}
$newVM1 = New-AzVM @vmParams

If they are not, I would like to create the VM with these two additional parameters.

Does anyone know how to do it in Powershell?

And which parameters on New-AzVM would you like to bind/map $dnsName and $reservedIP to, if present? — Mathias R. Jessen
– Mathias R. Jessen, Commented Aug 22, 2022 at 7:44
Yes, exactly @MathiasR.Jessen. I want these parametrs to be optional while creating VM — user346206
– user346206, Commented Aug 22, 2022 at 7:55
But which parameters? New-AzVM has neither a -dnsName nor a -reservedIP parameter defined? — Mathias R. Jessen
– Mathias R. Jessen, Commented Aug 22, 2022 at 9:13
@MathiasR.Jessen -PublicIpAddressName = $reservedIP and -DomainNameLabel = $dnsName — user346206
– user346206, Commented Aug 22, 2022 at 9:34
Inside the Hash for splatting, you do not use the hyphen in front of the parameter name — Theo
– Theo, Commented Aug 22, 2022 at 11:06

Mathias R. Jessen · Accepted Answer · 2022-08-22 11:22:09Z

1

Use a simple if statement to conditionally add entries to the splatting table:

if(-not [string]::IsNullOrWhiteSpace($dnsName)){
    $vmParams['DomainNameLabel'] = $dnsName
}

if(-not [string]::IsNullOrWhiteSpace($reservedIP)){
    $vmParams['PublicIpAddressName'] = $reservedIP
}

answered Aug 22, 2022 at 11:22

Mathias R. Jessen

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