Question

I’m using Powershell to set up IIS bindings on a web server, and having a problem with the following code:

$serverIps = gwmi Win32_NetworkAdapterConfiguration 
    | Where { $_.IPAddress } 
    | Select -Expand IPAddress 
    | Where { $_ -like '*.*.*.*' } 
    | Sort

if ($serverIps.length -le 1) {
    Write-Host "You need at least 2 IP addresses for this to work!"
    exit
}

$primaryIp = $serverIps[0]
$secondaryIp = $serverIps[1]

If there’s 2+ IPs on the server, fine – Powershell returns an array, and I can query the array length and extract the first and second addresses just fine.

Problem is – if there’s only one IP, Powershell doesn’t return a one-element array, it returns the IP address (as a string, like “192.168.0.100”) – the string has a .length property, it’s greater than 1, so the test passes, and I end up with the first two characters in the string, instead of the first two IP addresses in the collection.

How can I either force Powershell to return a one-element collection, or alternatively determine whether the returned “thing” is an object rather than a collection?

Answer 1

Define the variable as an array in one of two ways…

Wrap your piped commands in parentheses with an @ at the beginning:

$serverIps = @(gwmi Win32_NetworkAdapterConfiguration 
    | Where { $_.IPAddress } 
    | Select -Expand IPAddress 
    | Where { $_ -like '*.*.*.*' } 
    | Sort)

Specify the data type of the variable as an array:

[array]$serverIps = gwmi Win32_NetworkAdapterConfiguration 
    | Where { $_.IPAddress } 
    | Select -Expand IPAddress 
    | Where { $_ -like '*.*.*.*' } 
    | Sort

Or, check the data type of the variable…

IF ($ServerIps -isnot [array])
{ <error message> }
ELSE
{ <proceed> }