Accept Value From Pipeline Powershell Function

Question

I would like to create a script that tell the user whether or not PSRemoting is enabled on multiple remote machines. Here is what I have so far:

function Test-PSRemoting { Param( [Parameter(Mandatory=$True, ValueFromPipeline=$True)] [string[]] $ComputerName, [string] $Credential) $file = Read-Host "Enter file location for all error details: " try { $result = Invoke-Command -ComputerName $ComputerName -Credential $Credential { 1 } -ErrorAction SilentlyContinue -ErrorVariable Problem If ($Problem){ $result = 0} } catch { $result = 0} If ($result -eq 1){ write-host "PSRemoting is enabled on: " $ComputerName } else { write-host "PSRemoting is not enabled/working on: " $ComputerName $Problem | Out-File $file -Append} } 

The function works perfect if I only specify one computer:

Test-PSRemoting -ComputerName Server1 - Credentials Admin 

However, I cannot get the function to work if I specify multiple computers:

Test-PSRemoting -ComputerName Server1, Server2 - Credentials Admin Server1, Server2 | Test-PSRemoting -Credentials Admin 

Answer 1

I would use the Process{} block in this case (also answers your comment about why it was only checking Server2).

function test-ps { param( [Parameter(ValueFromPipeline=$true)] [string[]] $CN ) process{ Write-Host $CN "h" } } 'test1','test2' | test-ps 

http://ss64.com/ps/syntax-function-input.html

Answer 2

Try the following, comments below note key points.

function Test-PSRemoting { [CmdletBinding()] param ( [Parameter(Mandatory = $True, ValueFromPipeline = $True)] [string[]]$ComputerName, [Parameter(Mandatory = $False)] [System.Management.Automation.PSCredential]$Credential = (Get-Credential), [Parameter(Mandatory = $True)] [String]$OutFile ) process { # Pass computer name along the pipeline to allow for more then one. $ComputerName | % ` { $pcName = $_; $problem = $Null; try { $result = Invoke-Command -ComputerName $pcName -Credential $Credential { 1 } -ErrorAction SilentlyContinue -ErrorVariable problem; if ($problem -eq $Null -and $result -eq 1) { # Use Write-Verbose instead. Test-* commands are meant to return true/false. # But additional status can be viewed by adding the -Verbose parameter to Test-PSRemoting. i.e. Test-PSRemoting -Verbose Write-Verbose "PSRemoting is enabled on: $pcName"; return $True; } else { Write-Verbose "PSRemoting is not enabled/working on: $pcName"; $problem | Out-File $OutFile -Append; return $False; } } catch { return $False } } } } 

Key points are:

• Use of $ComputerName | to allow for Test-PSRemoting -ComputerName Server1,Server2 usage by handling you conditional logic per computer name specified. Invoke-Command naturally handles multiple computer names but your if statements do not.
• Moved $file to $OutFile parameter instead of Read-Host and marked as mandatory parameter to force input. Leaving Read-Host in a process { } block would mean that the file path is requested multiple times if Server1,Server2 | Test-PSRemoting is used. Also has the advantage of being able to be passed as a parameter instead of manually typed each time.
• Moved verbose output to Write-Verbose instead of Write-Host. Test-* commands should return True/False instead of a string. Use -Verbose to see verbose output. Additionally you could change the Write-Verbose "PSRemoting is not enabled/working on: $pcName"; line to a Write-Warning instead.