PowerShell variable within variable

Question

I am trying to add a variable $numberOfNics which adds nics based on the number. Right now this is my code, and I am a little confused as to how to put it into a loop. I know an array is probably the way to go but not quite sure how to make an array in this sense that just calls variables instead of sets them.

old code:

$numberOfNics=1

$networkname1 = "ondemandport1"
$networkname2 = "ondemandport2"
$networkname3 = "ondemandport3"
$networkname4 = "ondemandport4"
$networkname5 = "ondemandport5"
$networkname6 = "ondemandport6"
$networkname7 = "ondemandport7"
$networkname8 = "ondemandport8"
$networkname9 = "ondemandport9"

$networkInterface1 = New-AzureRmNetworkInterface -Name $networkname1

$networkInterface2 = New-AzureRmNetworkInterface -Name $networkname2 

$networkInterface3 = New-AzureRmNetworkInterface -Name $networkname3 

$networkInterface4 = New-AzureRmNetworkInterface -Name $networkname4 

$networkInterface5 = New-AzureRmNetworkInterface -Name $networkname5

To tidy this up, I would like to make a loop something like this

for ($i = 0; $i -lt $numberOfNics; $i++)
{
    $networkInterface$i = New-AzureRmNetworkInterface -Name $networkname$i
}

EDIT: Thanks Martin, but now I am having trouble calling the variable.

$networkInterfaces = 1 .. $numberOfNics | ForEach-Object { 
if ($a -eq 0){
    New-AzureRmNetworkInterface -ResourceGroupName $resourceGroupName -Name "ondemandport$_" -Location $locationName -SubnetId $virtualNetwork.Subnets[$a].Id -PublicIpAddressId $publicIp.Id -force
    }
ElseIf ($a=1){
    New-AzureRmNetworkInterface -ResourceGroupName $resourceGroupName -Name "ondemandport$_" -Location $locationName -SubnetId $virtualNetwork.Subnets[$a].Id -force
    }
Else{
    New-AzureRmNetworkInterface -ResourceGroupName $resourceGroupName -Name "ondemandport$_" -Location $locationName -SubnetId $virtualNetwork.Subnets[2].Id -force 
    }

}

#also looking to make this into a array loop

$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[1].Id -Primary
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[2].Id
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[3].Id
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[4].Id 
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[5].Id
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[6].Id
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[7].Id 
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[8].Id
$vmConfig = Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $networkInterfaces[9].Id

Error message: Add-AzureRmVMNetworkInterface : Cannot validate argument on parameter 'Id'. The argument is null or empty. Provide an argument that is not null or empty, and then try the command again.

Martin Brandl · Accepted Answer · 2018-02-07 06:27:47Z

3

You can also do it with one line:

$networkInterfaces = 1 .. $numberOfNics | ForEach-Object { New-AzureRmNetworkInterface -Name "ondemandport$_" }

Now you can access the interfaces by index, for example:

$networkInterfaces[2]

By the way, consider using ARM templates instead.

Edit:

$networkInterfaces = 1 .. $numberOfNics | ForEach-Object { 

    $isPrimary = $_ -eq 0 # set the first one as primary

    $nic = Get-AzureRmNetworkInterface -Name "ondemandport$_" -ResourceGroupName $resourceGroupName
    Add-AzureRmVMNetworkInterface -VM $vmConfig -Id $nic.Id -Primary:$isPrimary
}

edited Feb 7, 2018 at 6:27

answered Feb 6, 2018 at 6:26

Martin Brandl

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2 Comments

doggydogworld Over a year ago

Thanks Martin, the one liner worked well, and I've added it to my code, however, now I am having errors when calling the variable. I've edited my original post to show the error I am getting.

Martin Brandl Over a year ago

@doggydogworld The first interface would have index 0, maybe you get out of range here? However, you could try to use the Get-AzureRemNetworkInterface cmdlet to retrieve the nic, see my edited answer.

Owain Esau · Accepted Answer · 2018-02-06 06:19:52Z

0

You should be able to do something like this:

$numberOfNics= 10
$networkname = "ondemandport"

$networkInterface = @()

for ($i = 0; $i -le $numberOfNics; $i++)
{
    $networkInterface += ,@( New-AzureRmNetworkInterface -Name ($networkname + $i ))
}

Not sure if it will work with the New-AzureRmNetworkInterface but works with other New- commands

answered Feb 6, 2018 at 6:19

Owain Esau

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Comments

Vivek Kumar Singh · Accepted Answer · 2018-02-06 06:33:51Z

You could use PowerShell Get-Variable cmdlet. One thing which I would like to point out is the for loop which you are using will not be limited till $numberOfNics, but as a matter of fact, it's length will depend upon $networkname variable. For example, you are having networkname variables from $networkname1 to $networkname9, so your loop will look something like this -

$NetworkInfo = @()
for($i = 1; $i -le 9; $i++) {$NetworkInfo += Get-Variable("networkname" + $i)}

Now $NetworkInfo has

Name                           Value
----                           -----
networkname1                   ondemandport1
networkname2                   ondemandport2
networkname3                   ondemandport3
networkname4                   ondemandport4
networkname5                   ondemandport5
networkname6                   ondemandport6
networkname7                   ondemandport7
networkname8                   ondemandport8
networkname9                   ondemandport9

You can put another for loop something like this -

$NetworkInterface = @()
for ($i = 0; $i -lt $NetworkInfo.Length; $i++)
{
    $NetworkInterface +=  New-AzureRmNetworkInterface -Name $NetworkInfo.Value[$i]
}

Individual elements can then be accessed by $NetworkInterface[0], $NetworkInterface[1]... and so on.

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