Improved Answer - as long as you're OK with Start-Job instead of Start-Process
It turns out that the STDOUT and STDERR are accumulated in string arrays $job.ChildJobs[0].Output and $job.ChildJobs[0].Erroras the script runs. So you can poll these values and write them out periodically. Somewhat of a hack maybe, but it works.
It's not a stream though, so you have to manually keep track of the starting index into the array.
This code is simpler than my original answer, and at the end you have the entire STDOUT in $job.ChildJobs[0].Output. And as a little bonus for this demo, the calling script is PS7 and the background job is PS5.
$scriptBlock = {
Param ([int]$param1, [int]$param2)
$PSVersionTable
Start-Sleep -Seconds 1
$param1 + $param2
}
$parameters = @{
ScriptBlock = $scriptBlock
ArgumentList = 1, 2
PSVersion = 5.1 # <-- remove this line for PS7
}
$timeoutSec = 5
$job = Start-Job @parameters
$job.ChildJobs[0].Output
$index = $job.ChildJobs[0].Output.Count
while ($job.JobStateInfo.State -eq [System.Management.Automation.JobState]::Running) {
Start-Sleep -Milliseconds 200
$job.ChildJobs[0].Output[$index]
$index = $job.ChildJobs[0].Output.Count
if (([DateTime]::Now - $job.PSBeginTime).TotalSeconds -gt $timeoutSec) {
throw "Job timed out."
}
}
As pointed out, my original answer can interleave the output. This is a limitation of event handling in PowerShell. It's not a fixable problem.
Original Answer, don't use - just leaving it here for interest
If there's a timeout, ReadToEnd() is not an option. You could do some fancy looping, but IMO the 'cleanest' way to do this is to ignore the streams. Hook the OutputDataReceived/ErrorDataReceived events instead, collecting the output. This approach also avoids the threading issues mentioned by others.
This is straightforward in C#, but it's tricky and verbose in Powershell. In particular, add_OutputDataReceived is not available for some reason. (Not sure if this is a bug or a feature, at least this seems to be the case in PowerShell 5.1.) To work around it you can use Register-ObjectEvent.
$stdout = New-Object System.Text.StringBuilder
$stderr = New-Object System.Text.StringBuilder
$proc = [System.Diagnostics.Process]@{
StartInfo = @{
FileName = 'ping.exe'
Arguments = 'google.com'
RedirectStandardOutput = $true
RedirectStandardError = $true
UseShellExecute = $false
WorkingDirectory = $PSScriptRoot
}
}
$stdoutEvent = Register-ObjectEvent $proc -EventName OutputDataReceived -MessageData $stdout -Action {
$Event.MessageData.AppendLine($Event.SourceEventArgs.Data)
}
$stderrEvent = Register-ObjectEvent $proc -EventName ErrorDataReceived -MessageData $stderr -Action {
$Event.MessageData.AppendLine($Event.SourceEventArgs.Data)
}
$proc.Start() | Out-Null
$proc.BeginOutputReadLine()
$proc.BeginErrorReadLine()
Wait-Process -Id $proc.Id -TimeoutSec 5
if ($proc.HasExited) {
$exitCode = $proc.ExitCode
}
else {
Stop-Process -Force -Id $proc.Id
$exitCode = -1
}
# Be sure to unregister. You have been warned.
Unregister-Event $stdoutEvent.Id
Unregister-Event $stderrEvent.Id
Write-Output $stdout.ToString()
Write-Output $stderr.ToString()
Write-Output "Exit code: $exitCode"
- The code shown is the happy path (stderr is empty)
- To test the timeout path, set
-TimeoutSec to .5
- To test the sad path (stderr has content), set
FileName to 'cmd' and Arguments to /C asdf
