Using Get-Job to test-connection, but quite different

Question

It's my first post here, I'm tring to write scripts on PS on my own, now my target is to write script that checks if computer is online at network, for example: test-Connection 192.168.0.1, 2, 3 etc. Doing this one by one on loop for takes some time if some computers are offline, I've found some tutorials on this site to use -AsJob param, but I'm not really Sure how could it work. I mean I'd like to output every checked PC to excel, so i need if operator. eg:

if (Job1 completed successfull (computer pings)){ do smth}...

I need to get output from Job boolean (true/false), but one by one. I'm taking my first steps in PS, I've made program that checks it one by one in for loop, but as i said it take some time till my excel file fill...

I can see, that AsJob makes working more effective and I think it's important to understand it

Thanks and sorry for bad text formatting, by the time I'll go on with this!

Answer 1

In your example, in the Start-Job scriptblock you are trying to access $_ which is not available in the codeblock scope. If you replace $_ with $args[0] it should work since you are passing in the $ip value as an argument

Your Example

$ipki = Get-Content 'C:\Users\pchor\Desktop\ipki.txt'
foreach ($ip in $ipki) {
    Start-Job -Name "$ip" -ScriptBlock {
        Test-Connection $_ -Count 1  # <---- replace $_ with $args[0]
    } -ArgumentList $_  # <----- change $_ to $ip 
}

You'll probably also want to wait for all the jobs to finish. I recommend something like this

$computers = @(
    'www.google.com'
    'www.yahoo.com'
)

$jobs = $computers |
    ForEach-Object {
        Start-Job -ScriptBlock {
            [pscustomobject]@{
                Computer = $using:_
                Alive    = Test-Connection $using:_ -Count 1 -Quiet
            }
        }
    }

# Loop until all jobs have stopped running
While ($jobs |
        Where-Object { $_.state -eq 'Running' }) {
    "# of jobs still running $( ($jobs | Where-Object {$_.state -eq 'Running'}).Count )";
    Start-Sleep -Seconds 2
}
$results = $jobs | Receive-Job | Select-Object Computer, Alive
$results | Format-Table

Output

Computer       Alive
--------       -----
www.google.com  True
www.yahoo.com   True

To modify the properties to what you want there are different ways of doing this. Easiest in this case is probably to use a calculated property

$newResults = $results | 
    Select-Object Computer, 
    @{Label = 'State'; Expression = { if ($_.Alive) { 'Online' } else { 'Offline' } } }

Objects will now look like this (I added another fake address to illustrate offline state)

Computer                 State
--------                 -----
www.google.com           Online
www.yahoo.com            Online
xxx.NotAValidAddress.xxx Offline

You can then export the objects to csv using Export-csv

$newResults | Export-Csv -Path c:\temp\output.csv