如何从Powershell作业捕获.NET跟踪输出？

Question

I am using a .NET component in Powershell which uses Trace.TraceWarning , Trace.TraceInformation etc.

I want to output these traces to the console when I run my Powershell script.

This works when I use the component in the current session. For example (simulating the effect of trace) gives me 'Hello' output to the console:

 $listener = new-object "system.diagnostics.consoletracelistener"
 [System.Diagnostics.Trace]::Listeners.Add($listener) | Out-Null
 [System.Diagnostics.Trace]::TraceInformation("Hello")

But if I do the same within a Powershell job I get no output, even though ConsoleTraceListener should be writing to STDOUT which in turn I expected to get captured by the job. (Interestingly Console.WriteLine doesn't work from a job either - but Write-Host does).

I am starting my job like so:

$work = {
     $listener = new-object "system.diagnostics.consoletracelistener"
     [System.Diagnostics.Trace]::Listeners.Add($listener) | Out-Null
     [System.Diagnostics.Trace]::TraceInformation("Hello")
}
$job = Start-Job -RunAs32 -ScriptBlock $work
$job | Receive-Job -Wait

Answer 1

It's not clear where you want the captured output to go. Most of the discussion so far revolves around the Console, but since you called it a "job" (I presume you mean Scheduled Task), I'm not so sure the Console is the best place. You'd never see the results. A log file sounds much more appropriate. If that's the case, you should create a TextWriteTraceLister . That will allow you to set a log file for the results.

Additionally, one of the nice features of Tracing in .Net is that you can have more than one listener attached. So if you want to see the output as it runs, you can also attach the ConsoleTraceListener, and it won't interfere with writing to the log file.

Finally, it's also possible to write your own TraceListener. This is useful for things like writing to a logging database or web service. To use your own TraceListener from PowerShell, you would need to build the listener using a .Net language that can be compiled into a class library assembly (dll) that can be deployed to the GAC for use in your project.

Answer 2

I remember running into something similar to this years ago where expected STDOUT and STDIN weren't behaving as expected with start-job and exe's. I ended up using System.Diagnostics.Process and redirecting the STDIN and STDOUT. Here's an example that demonstrates this workaround in a way that may assist you with what you are trying to do.

#added extra trace messages with Get-Date and implemented a random delay for demo purpose
$work = {
     $listener = new-object "system.diagnostics.consoletracelistener"
     [System.Diagnostics.Trace]::Listeners.Add($listener) | Out-Null
     1..10 | % {
         Start-Sleep $(Get-Random 5)
         [System.Diagnostics.Trace]::TraceInformation((Get-Date))
    }
}
#Create a process
$process = New-Object System.Diagnostics.Process 
$process.StartInfo.UseShellExecute = $false
#redirect stdout
$process.StartInfo.RedirectStandardOutput = $true
#call powershell
$process.StartInfo.FileName = "powershell.exe"
#pass the $work scriptblock
$process.StartInfo.Arguments = "-noprofile -command $work"
#start the process
$process.Start() | Out-Null
#readlines as they come in and exit when process is done
while(-not $process.HasExited){
    $process.StandardOutput.ReadLine()
}

Output:

powershell.exe Information: 0 : 01/30/2015 12:27:17
powershell.exe Information: 0 : 01/30/2015 12:27:20
powershell.exe Information: 0 : 01/30/2015 12:27:21
powershell.exe Information: 0 : 01/30/2015 12:27:25
powershell.exe Information: 0 : 01/30/2015 12:27:26
powershell.exe Information: 0 : 01/30/2015 12:27:28
powershell.exe Information: 0 : 01/30/2015 12:27:29
powershell.exe Information: 0 : 01/30/2015 12:27:33
powershell.exe Information: 0 : 01/30/2015 12:27:36
powershell.exe Information: 0 : 01/30/2015 12:27:40