Using a powershell object to execute scripts

Question

Powershell Version Used: 3.0

Hello everybody,

I am trying to create a new Powershell pipeline and execute the script inside it, and then get the output it produces into the output variable, but I cannot get any result created inside the object (from the executed script). The thing is that I do not need to manage the $ Error object, which I intend to use to detect errors. Here is an example below:

$ps = [Powershell]::Create() $File = ".\Test2.ps1" $SortedParams = "-Name blah -Key foo" $RootDirectory = Get-Location $ExecutionDirectory = "$RootDirectory\Test3" $ps.AddCommand("Set-Location").AddParameter("Path", "$ExecutionDirectory") write-host "COMMAND 1: " $ps.Commands.Commands.Item(0).CommandText $ps.AddScript("$File $SortedParams") write-host "COMMAND 2: " $ps.Commands.Commands.Item(1).CommandText $output = $ps.Invoke() write-host $output 

I should mention that I am trying to use the following 3 methods to create output in a script:

• Write host
• Write output
• Write-Verbose (uses $ ps.Streams.Verbose to try to get the result, but nothing)

Any suggestions or tips you can give are greatly appreciated!

Answer 1

If you don’t feel the need to do things the way you do them, you may need to use PowerShell background jobs instead.

Background jobs let you run PowerShell commands in a separate PowerShell instance, and then collect the output from these jobs into a variable (if that's what you want to do).

See the about_Jobs help topic for more information.

Here is an example:

 $job = Start-Job -ScriptBlock { "Hello World!" } $ret = Receive-Job $job -Wait -AutoRemoveJob # value of $ret will be "Hello World!" 

Answer 2

You can invoke another script using the Invoke-Expression cmdlet and write its output using the -OutVariable parameter. I recommend using Out-Null so that the data does not populate the console twice, feel free to delete this command. Here is an example:

 Invoke-Expression -Command "c:\EventLog.ps1" -OutVariable $data | Out-Null Write-Host $data 

This is the code from the sample script that I used in the above example:

 Param($ComputerName = ".") Get-EventLog -ComputerName $ComputerName -Log application -EntryType Error | Group-Object -Property source | Sort-Object -Property Count -Descending | Format-Table Count, Name -AutoSize 

Answer 3

Check your error stream for errors:

 $ps.Streams.Error 

This worked for me:

 $ps = [Powershell]::Create() cd 'C:\Users\Andy\Documents' $File = ".\Test2.ps1" $SortedParams = "-Name blah -Key foo" $RootDirectory = Get-Location $ExecutionDirectory = "$RootDirectory\Test3" $ps.AddCommand("Set-Location").AddParameter("Path", "$ExecutionDirectory") | Out-Null $ps.AddScript("$File $SortedParams") | Out-Null $output = $ps.Invoke() write-host $output 

This shows my setup:

Show file organization:

 Command: tree.com /F /A $ExecutionDirectory Output: C:\USERS\ANDY\DOCUMENTS\TEST3 Test2.ps1 

Show script contents:

 Command: cat "$ExecutionDirectory\Test2.ps1" Output: param ( $Name, $Key ) $Name $Key 

Answer 4

I am using Invoke-Expression and this is the only solution that works for me:

test2.ps

 Invoke-Expression .\test1.ps1 | Tee-Object -Variable msg | Out-Null write-host "Return: $msg"</code> 

And test1.ps:

 $hola="Testing" $hola 

Call:

 C:\Test>powershell -ExecutionPolicy unrestricted -file test2.ps1 Return: Testing