logic for powershell for-each loop

Question

I was using below powershell script to loop thru servers in the list to perform particular tasks depending upon the server's hostname. In the below script if $server = 'server1' I want to perform different set of tasks in contrast to other servers, But this loop is directly executing 'else' loop. I'm I missing anything here?

$servernames = @("server1", "server2", "server3")
$user = '**********'
$Password = '*******'
$SecurePassword = $Password | ConvertTo-SecureString -AsPlainText -Force
$cred = New-Object System.Management.Automation.PSCredential -ArgumentList $user, $SecurePassword

foreach($server in $servernames)
{
    Invoke-Command -ComputerName $server -Credential $cred -ScriptBlock {          
        if ($server -eq 'server1')
        {
            #do some task on server1
        }
        else
        {
            #do tasks for remaining servers
        }
    } 

    if ($error) { exit 1 }
}

BenH · Accepted Answer · 2017-08-29 16:00:56Z

1

Since $Server is inside the script block of the invoke command, it doesn't exist in that scope. You could pass it with -Argumentlist or the "using" scope (PS3+) e.g. if ($using:server -eq 'server1') But likely makes more sense, to put the if statement outside of the Invoke-Command.

if ($server -eq 'server1') {
    Invoke-Command -ComputerName $server -Credential $cred -ScriptBlock { 
        "Stuff to do on Server1"
    }
} else { "Other Servers"}

answered Aug 29, 2017 at 16:00

BenH

10.1k1 gold badge26 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Maximilian Burszley · Accepted Answer · 2017-08-29 16:01:06Z

1

Your scriptblock is in a different scope and doesn't see $server. I'd suggest figuring out your logic before executing the command.

If ($Server -eq 'server1')
{ Invoke-Command -ComputerName $Server -Credential $Cred -ScriptBlock {} }

answered Aug 29, 2017 at 16:01

Maximilian Burszley

19.9k7 gold badges39 silver badges68 bronze badges

Comments

Bacon Bits · Accepted Answer · 2017-08-29 16:06:40Z

0

The value for the $server variable goes out of scope once it gets passed to the remote system. To prevent that from happening, you need to pass the parameters you need. To do that, you treat the script block you use as a function and define parameters for it, and then use the ArgumentList parameter of Invoke-Command to pass the values:

foreach ($server in $servernames) {
    Invoke-Command -ComputerName $server -Credential $cred -ScriptBlock {          
        Param($server)
        if ($server -eq 'server1') {
            #do some task on server1
        }
        else {
            #do tasks for remaining servers
        }
    } -ArgumentList $server

    if ($error) { exit 1 }
}

To be a little more clear about what's happening, I'll rename the parameter that the script block uses:

foreach ($server in $servernames) {
    Invoke-Command -ComputerName $server -Credential $cred -ScriptBlock {          
        Param($MyServer)
        if ($MyServer -eq 'server1') {
            #do some task on server1
        }
        else {
            #do tasks for remaining servers
        }
    } -ArgumentList $Server

    if ($error) { exit 1 }
}

answered Aug 29, 2017 at 16:06

Bacon Bits

32.5k6 gold badges64 silver badges79 bronze badges

2 Comments

workholic Over a year ago

Thanks for all the suggestions; In addition to that I had a unzip function which needs to be executed on all the servers in the list using invoke-command. Is there any better way to do rather than declaring unzip function inside invoke-command loop for each server? Add-Type -AssemblyName System.IO.Compression.FileSystem function Unzip { param([string]$zipfile, [string]$outpath) [System.IO.Compression.ZipFile]::ExtractToDirectory($zipfile, $outpath) }

Bacon Bits Over a year ago

@workholic No, you will need to declare the function in the remote session somehow. The remote session is completely distinct from the local one. The only things that get passed to it are what you explicitly pass to it.

Collectives™ on Stack Overflow

logic for powershell for-each loop

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related