Using PowerShell, how can I use Substring to extract the computer name from output

Question

I am new to PowerShell but I found I can use Substring to count to the right or left of a string within a variable. It appears though it is not supported for the output I am receiving. I am hoping someone can point me in the right direction. Thank you for any help.

Code to retrieve the computer name.

$compname = WmiObject -class Win32_ComputerSystem | Select-Object Name
$compname
$compname.Substring(9,0)

Here is the result and error:

Name

Computer-PC Method invocation failed because [Selected.System.Management.ManagementObject] does not contain a method named 'Substring'. At line:3 char:1

$compname.Substring(9,0)

  + CategoryInfo          : InvalidOperation: (Substring:String) [], RuntimeException
  + FullyQualifiedErrorId : MethodNotFound

You don't need sub string, use $compname = WmiObject -class Win32_ComputerSystem | ForEach-Object Name or $compname = (WmiObject -class Win32_ComputerSystem).Name — zett42
– zett42, Commented Jun 9, 2022 at 18:07
$compname = WmiObject -class Win32_ComputerSystem | Select-Object -ExpandProperty Name should give you a [System.String], and [System.String] has the method you're looking for. Also, check out the environment variable $env:COMPUTERNAME. — notjustme
– notjustme, Commented Jun 9, 2022 at 18:07
Thank you both for your input. I think I will be going with Zett42, ForEach-Object. It works great. The output is clean how I need it. I looked a long time and never found anything like this. It will also help with some other code I have as well. Thanks a million. I just checked the other option and what notjustme gave and they all have the same results. Thanks again. — Jonathan Blaine
– Jonathan Blaine, Commented Jun 9, 2022 at 18:38

Robert Wyllyam · Accepted Answer · 2022-06-09 22:07:28Z

1

This error occurs because you're trying to use the Substring method on an object.

Take a look, if i do the same query that you did, it returns me an object with "Name" property:

And as the powershell error shows, you cannot call the substring method directly to an object. You must do it on a string, in this case, the property name. To solve you problem, you just need to call "Name" property in your query. Something like this:

$computerName = (Get-WmiObject Win32_ComputerSystem).Name

After that, you will be able to use "Substring" method because that query returns a string:

If any other problem occurs, i will be glad to help you :)

answered Jun 9, 2022 at 22:07

Robert Wyllyam

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Jonathan Blaine Over a year ago

Thank you Robert for this information, zett42 gave the same answer to use "$computerName = (Get-WmiObject Win32_ComputerSystem).Name" which I've accepted. Thank you for explaining that a Substring cannot be used on an object. I have a lot to learn about PowerShell.

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