Question

I want to start a Java program from PowerShell and get the results printed on the console.

I have followed the instructions of this question:
Capturing standard out and error with Start-Process

But for me, this is not working as I expected. What I’m doing wrong?

This is the script:

$psi = New-object System.Diagnostics.ProcessStartInfo
$psi.CreateNoWindow = $true
$psi.UseShellExecute = $false
$psi.RedirectStandardOutput = $true
$psi.RedirectStandardError = $true
$psi.FileName = 'java.exe'
$psi.Arguments = @("-jar","tools\compiler.jar","--compilation_level",   "ADVANCED_OPTIMIZATIONS", "--js", $BuildFile, "--js_output_file", $BuildMinFile)
$process = New-Object System.Diagnostics.Process
$process.StartInfo = $psi
$process.Start() | Out-Null
$process.WaitForExit()
$output = $process.StandardOutput.ReadToEnd()
$output

The $output variable is always empty (and nothing is printed on the console of course).

Answer 1

The docs on the RedirectStandardError property suggests that it is better to put the WaitForExit() call after the ReadToEnd() call. The following works correctly for me:

$psi = New-object System.Diagnostics.ProcessStartInfo 
$psi.CreateNoWindow = $true 
$psi.UseShellExecute = $false 
$psi.RedirectStandardOutput = $true 
$psi.RedirectStandardError = $true 
$psi.FileName = 'ipconfig.exe' 
$psi.Arguments = @("/a") 
$process = New-Object System.Diagnostics.Process 
$process.StartInfo = $psi 
[void]$process.Start()
$output = $process.StandardOutput.ReadToEnd() 
$process.WaitForExit() 
$output