I have about 20 files, each one of them contains IPs.
I have a function that uploads the IPs to rules I have in azure. Script will work just fine if running one by one but I need it to be parallel.

$i=1
foreach ($file in  (gci . -name "auto_farm_protection_*") ){
    Start-Job -ScriptBlock {
        [string[]]$ipsarry = Get-Content $file

        az network nsg rule update -g Testim --nsg-name sg-test -n "test_$i" --source-address-prefix $ipsarry 
            
    } -ArgumentList file,i 

    $i++ 
}

Should read "test_1" and pass it, "test_2" and pass it and so on.
For some reason arguments do not pass to the start-job part, but I do use -ArgumentsList.

>Solution :

It’s probably faster with start-threadjob from the powershell gallery, or foreach-object -parallel in powershell 7. You’ll need the full path of the files you open too, since unfortunately jobs use a default ~\documents directory (threadjobs don’t have this problem). I’ve double quoted the az command as a demo since I don’t have it.

# echo 192.168.1.1 > auto_farm_protection_a
# echo 192.168.1.2 > auto_farm_protection_b
# Install-Module -Name ThreadJob

$i=1
$result = foreach ($file in (gci . "auto_farm_protection_*") ){
    Start-ThreadJob -ScriptBlock {
        param($file, $i)
        [string[]]$ipsarry = Get-Content $file.fullname
        "az network nsg rule update -g Testim --nsg-name sg-test -n test_$i --source-address-prefix $ipsarry"
    } -Argumentlist $file,$i 
    $i++ 
}
$result | receive-job -wait -autoremove


az network nsg rule update -g Testim --nsg-name sg-test -n test_1 --source-address-prefix 192.168.1.1
az network nsg rule update -g Testim --nsg-name sg-test -n test_2 --source-address-prefix 192.168.1.2