PowerShell Exception calling “Start” with “0” argument(s) from within another function

Question

I am writing my first Powershell script and coming from C# am confused, my code is below:

function Run(
[string] $command,
[string] $args,
[Ref] [string] $stdout,
[Ref] [string] $stderr
)
{  
    $p1 = New-Object System.Diagnostics.Process
    $p1.StartInfo = New-Object System.Diagnostics.ProcessStartInfo;
    $p1.StartInfo.FileName = $command
    $p1.StartInfo.Arguments = $arguments
    $p1.StartInfo.CreateNoWindow = $true
    $p1.StartInfo.RedirectStandardError = $true
    $p1.StartInfo.RedirectStandardOutput = $true
    $p1.StartInfo.UseShellExecute = $false

    $p1.Start()
    $p1.WaitForExit()
}

$p = New-Object System.Diagnostics.Process
$p.StartInfo = New-Object System.Diagnostics.ProcessStartInfo;
$p.StartInfo.FileName = "ping"
$p.StartInfo.Arguments = "142.553.22242.2"
$p.StartInfo.CreateNoWindow = $true
$p.StartInfo.RedirectStandardError = $true
$p.StartInfo.RedirectStandardOutput = $true
$p.StartInfo.UseShellExecute = $false

$p.Start()
$p.WaitForExit()
$code = $p.ExitCode
$stderr = $p.StandardError.ReadToEnd()
$stdout = $p.StandardOutput.ReadToEnd()


Run("ping","208.67.222.222","","")

The $p.Start() works, but for some reason the parameters passed in to the Run function are ignored and $p1 fails. What am I doing wrong please?

Exception calling "Start" with "0" argument(s): "The system cannot find the file specified"
At C:\Users\Administrator\Desktop\logtofile.ps1:27 char:5
+     $p1.Start()
+     ~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : Win32Exception

Exception calling "WaitForExit" with "0" argument(s): "No process is associated with this object."
At C:\Users\Administrator\Desktop\logtofile.ps1:28 char:5
+     $p1.WaitForExit()
+     ~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : InvalidOperationException

Answer 1

I wasn't trying to start a process from inside a function, but I was getting the same error. It took me a few minutes to realize that it was one of my favorite time-wasters: a UAC trap. I hadn't started PowerShell using "Run as administrator". You have to have admin privileges and run the code as such to start/stop/modify processes that you don't own and this error message is totally unhelpful in this regard.

Answer 2

You have to call run as follows:

Run "ping","208.67.222.222","",""

putting in between the parentheses passes it to the function as a single array argument.

Answer 3

function Demo  {
    param (
        $fileName,$Arguments
    )

    $p = New-Object System.Diagnostics.Process
    $p.StartInfo = New-Object System.Diagnostics.ProcessStartInfo
    $p.StartInfo.FileName = $fileName
    $p.StartInfo.RedirectStandardError = $true
    $p.StartInfo.RedirectStandardOutput = $true
    $p.StartInfo.UseShellExecute = $false
    $p.StartInfo.Arguments = $Arguments
    $p.Start() | Out-Null
    $p.WaitForExit()

    $stdout = $p.StandardOutput.ReadToEnd()
    $stderr = $p.StandardError.ReadToEnd()
    Write-Host "stdout: $stdout"
    Write-Host "stderr: $stderr"
    Write-Host "exit code: " + $p.ExitCode
}

Demo "getmac" " /v"

Answer 4

I got this error with the start() function on a service because a colleague set the service to "disabled" in the Windows Services window. Setting it back to "Manual" fixed it.