How do I write a script to reboot a list of servers, but will EXCLUDE servers I don't want rebooted?

Question

Being new to PowerShell I've been following some of the guidance in these posts to write a script for what's mentioned in the subject.

Here's the script:

Get-Content -Path C:\temp\Domain.txt | Restart-Computer -force | Where-Object { $._Name -notmatch "^(SERVER01)"}

Here's the error:

Restart-Computer : Cannot validate argument on parameter 'ComputerName'. The argument is null or empty. Provide an argument that is not null or empty, and then try the command again.
At line:1 char:40
+ ... et-Content -Path C:\temp\Domain.txt | Restart-Computer -force | Where ...
+                                           ~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidData: (:PSObject) [Restart-Computer], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.PowerShell.Commands.RestartComputerCommand

For reference, the DOMAIN.txt has a list of servers that will periodically change so I want to skip certain servers should they end up on the list.

Answer 1

The error simply means you have an empty line on your text file, you can filter the lines using .Where(..) method and exclude empty or white space lines with the help of [string]::IsNullOrWhiteSpace(..) method. I have changed -notmach for the containment operator -notin.

Note, -notin looks for an exact match within the collection $hostsToExclude.

$hostToExclude = 'server1', 'server2'
(Get-Content -Path C:\temp\Domain.txt).Where({
    -not [string]::IsNullOrWhiteSpace($_) -and $_ -notin $hostToExclude
}) | Restart-Computer -Force

It's worth noting that, on your snippet, you're restarting the hosts before filtering the collection. Get-Content should be followed by Where-Object.