Variable is array instead of string? - powershell

Question

I wrote this small script and when I test Write-Host $serial it appears fine, but when it is running in the background $serial seems to contain an array.
It tries to rename computer to C000#{SerialNumber=F7ZL3F2} instead of just C000F7ZL3F2.
What should I do to just get string not this array?
Import-Module ActiveDirectory
Get-ADComputer -Filter {Name -like 'DESKTOP-*'} -Properties * | Select Name, DNSHostName | ForEach-Object {
$rtn = Test-Connection -CN $_.dnshostname -Count 1 -BufferSize 16 -Quiet
if ($rtn -match 'True') {
$serial = Get-WMIObject Win32_Bios -ComputerName $_.name | Select-String SerialNumber
$serial = "C000$serial"
// Write-Host $serial
Rename-Computer -ComputerName $_.name -NewName $serial -DomainCredential $mycreds -Force -Restart
}
}

Answer 1

There are two mistakes to be pointed out in your code -
$serial = Get-WMIObject Win32_Bios -ComputerName $_.name | Select-String SerialNumber
The Select-String cmdlet searches for text and text patterns in input strings and files. Where as the basetype output of Get-WMIObject Win32_Bios is System.Management.ManagementBaseObject
(Get-WMIObject Win32_Bios).Gettype()
IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True ManagementObject System.Management.ManagementBaseObject
In such cases, instead of Select-String, you can use Select-Object to choose amongst the properties. Since, Serial Number is one of the properties returned by your input command.
$serial = "C000$serial"
The output of $serial will be something like this:
SerialNumber
5CXXXXYYYXZZZ
Again, you can call it directly by $serial.SerialNumber. So your overall code will be
Import-Module ActiveDirectory
Get-ADComputer -Filter {Name -like 'DESKTOP-*'} -Properties * | Select Name, DNSHostName | ForEach-Object {
$rtn = Test-Connection -CN $_.dnshostname -Count 1 -BufferSize 16 -Quiet
if ($rtn -match 'True') {
$serial = Get-WMIObject Win32_Bios -ComputerName $_.name |
Select-Object SerialNumber
$serial = "C000$($serial.SerialNumber)"
Rename-Computer -ComputerName $_.name -NewName $serial -DomainCredential $mycreds -Force -Restart
}
}
Or you can use -ExpandProperty parameter of the Select-Object cmdlet like
$serial = Get-WMIObject Win32_Bios -ComputerName $_.name |
Select-Object -ExpandProperty SerialNumber
$serial = "C000$serial"

Answer 2

Try changing this line:
$serial = Get-WMIObject Win32_Bios -ComputerName $_.name |
Select-String SerialNumber
to this:
$serial = (Get-WMIObject Win32_Bios -ComputerName $_.name).SerialNumber
or this:
$serial = Get-WMIObject Win32_Bios -ComputerName $_.name |
Select-Object -ExpandProperty SerialNumber

Answer 3

Why are you using Select-String? I would use Select-Object and then -ExpandProperty
Import-Module ActiveDirectory
Get-ADComputer -Filter {Name -like 'DESKTOP-*'} -Properties * | Select Name, DNSHostName | ForEach-Object {
$rtn = Test-Connection -CN $_.dnshostname -Count 1 -BufferSize 16 -Quiet
if ($rtn -match 'True') {
$serial = Get-WMIObject Win32_Bios -ComputerName $_.name | Select-Object -ExpandProperty SerialNumber
$serial = "C000$serial"
// Write-Host $serial
Rename-Computer -ComputerName $_.name -NewName $serial -DomainCredential $mycreds -Force -Restart
}
}