Comments on: PowerShell Script: Select-Alive

By: Episode 49 - Susan Bradley the SBS Diva « PowerScripting Podcast

Episode 49 - Susan Bradley the SBS Diva « PowerScripting Podcast — Mon, 17 Nov 2008 03:30:05 +0000

[...] how to build functions which can be used in a pipeline. Hal wrote a script a while ago called Select-Alive which serves as a good [...]

By: Jarmo

Jarmo — Wed, 23 Jan 2008 07:34:15 +0000

Thanks for the script.
I have made some corrections/additions:

Line 4: change $computer to $cn

Line 25(not bug, but a nice addition):

“PSCustomObject” { if ($obj.cn) { $cn = $obj.cn} else { $cn = $obj.Name } }

Lines 32-34: Current script is very quiet, if computer has an ip address, but does not respond, so I added else statement:

if ($reply.status -eq “Success”) {
$cn; $pingCount++
} else {
Write-Verbose “$(get-date -f ‘s’) ping $($reply.status): $cn”
}

By: TechProsaic - I write about great software, Internet technology, cool gadgets, and The Next Big Thing. » Solving Problems with PowerShell: Simple Benchmarking

Wed, 28 Nov 2007 18:16:36 +0000

[...] PowerShell Script: Select-Alive [...]

By: halr9000

halr9000 — Mon, 05 Nov 2007 13:27:45 +0000

Thanks for the comments Kirk. No, the default function scope is such that my changes to those global variables don’t stick. At least that’s what my testing has shown. Try it yourself, check the value of those before and after running my function.

Changing subjects, I’m thinking of expanding this function to include an RPC ping for when ICMP isn’t desirable, and maybe an WinRM check as well. Or that might be a separate function.

By: Kirk Munro

Kirk Munro — Mon, 05 Nov 2007 12:48:08 +0000

Hi Hal,

I was just looking this filter over and I think it’s missing something (but I don’t have time to test it right now to verify that). Correct me if I’m wrong, but isn’t this script permanently changing the values of $verbosePreference and $errorActionPreference such that the changes are retained after the filter has exited? Wouldn’t it be better to store the current values when you enter the filter, set them based on the switch parameter, and then reset to their original values before you exit? Otherwise you might cause unexpected behaviour in some users environments after they’ve used this filter, no?

Kirk out.