How to show real-time output by running a PowerShell Script?

Question

I am trying to run powershell script from VB and I want to see the output of the script as it is running inside a console application. With my script (shown below) when I run from powershell it shows "Command Sleep Starting" and then waits for 5 seconds and then displays the other text.

However, when I run from VB.NET program, the execution waits for 5 seconds and dumps all the text output at once. It doesn't execute first Write-Output command and then wait and then output as it should.

Write-Output "Command Sleeping Starting"
Start-Sleep -Seconds 5
Write-Output "Command ran successfully"

Any idea on how to show real-time execution output when I run the script from VB .Net Program?

Just for more info below is the code I used.

            Dim start As New ProcessStartInfo
            Dim ScriptsFolder As String = GetKeyValue("ScriptsFolder")
            Console.WriteLine(ScriptsFolder.ToString())
            start.FileName = "powershell.exe"
            start.Arguments = ScriptsFolder + "\" + ScriptFile
            start.UseShellExecute = False
            start.RedirectStandardOutput = True
            start.RedirectStandardError = True

            Dim myproc As New Process
            myproc.StartInfo = start
            myproc.Start()
            Dim so As System.IO.StreamReader
            Dim se As System.IO.StreamReader
            se = myproc.StandardError
            so = myproc.StandardOutput
            myproc.WaitForExit()
            Console.WriteLine(so.ReadToEnd)
            Console.WriteLine(se.ReadToEnd)

Someone was trying to do this with Java. I'm not sure stdout can be read until the process exits.. — Andy Arismendi
– Andy Arismendi, Commented Mar 1, 2012 at 22:07

Nick Nieslanik · Accepted Answer · 2012-03-01 23:30:04Z

4

Have you considered executing a PowerShell runspace programmatically using the System.Windows.Automation namespaces rather than starting the process? You can then pass in a logger object to the pipeline and log to it, displaying the messages in realtime.

Here is a simple snippet for spinning up a Runspace in VB.NET

    ' create Powershell runspace 
    Dim MyRunSpace As Runspace = RunspaceFactory.CreateRunspace()

    ' open it 
    MyRunSpace.Open()

    ' create a pipeline and feed it the script text 
    Dim MyPipeline As Pipeline = MyRunSpace.CreatePipeline()

    MyPipeline.Commands.AddScript(scriptText)

    ' pass in a logger object you can use instead of Write-Output
    MyPipeline.Runspace.SessionStateProxy.SetVariable("logger", SomeLoggerObject) 

    ' execute the script 
    Dim results As Collection(Of PSObject) = MyPipeline.Invoke()

    ' close the runspace 
    MyRunSpace.Close()

answered Mar 1, 2012 at 23:30

Nick Nieslanik

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3 Comments

Andy Arismendi Over a year ago

Agree with this. Instead of invoking PowerShell.exe, just use the API :-)

Mitul Over a year ago

I do agree the above approach is the way to run powershell command but I am sorry that my question was not that. I wanted to know if we could show incremental output as the script is running. Will this approach show incremental output?

Nick Nieslanik Over a year ago

If you pass in a logger object to your script and then replace the write-output calls with calls to your logger, then the ability to show real-time data from your logger will depend on it's implementation. An Example would be a TraceListener model where you could subscribe any listener you wish and visualize the logging output anyway you want.

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