Hi

I found a number of articles on running processes and BAT files and capturing the output and errors, e.g.

http://www.chinabtp.com/captured-output-of-command-run-by-powershell-is-sometimes-incomplete/
http://stackoverflow.com/questions/24370814/how-to-capture-process-output-asynchronously-in-powershell

So I created a test function below and it "works"
However I wanted to have control over the display of the output, i.e. close to real time. According to the doco the event gets fired for each newline, my tests indicate otherwise.
i.e. the script may run for a long time and have 1000s of lines of output..

I did a test where I told the BAT file to sleep. However the results where not as expected.
There was a delay until the first output occurred, then a further delay which could be accounted for due to the sleep.

https://msdn.microsoft.com/en-us/library/microsoft.powershell.utility.activities.registerobjectevent_methods(v=vs.85).aspx
https://msdn.microsoft.com/en-us/library/microsoft.powershell.utility.activities.registerobjectevent_members(v=vs.85).aspx

Don't help because there are poorly documented, e.g. MaxtriggerCount, provides access to maxtriggercount, none of the items are actually described by function.

The C# process has ReadToEnd() but this does not apply to Powershell

So the question :

>> Is there a way for me fetch the output event data, say in the 1s while loop ?

SBS_Logger justs adds the timestamp

Function SBS_RunAProcess
{
[CmdletBinding()]
 param(
 		[Parameter(Mandatory = $True)] 
       [String]$Label )
	   
		# Setup stdin\stdout redirection
		$StartInfo = New-Object System.Diagnostics.ProcessStartInfo -Property @{
			FileName = "F:\ScriptWork\helloworld.bat"
			Arguments = $Label
			UseShellExecute = $false
			RedirectStandardOutput = $true
			RedirectStandardError = $true
		}
		# Create new process
		$Process = New-Object System.Diagnostics.Process
		# Assign previously created StartInfo properties
		$Process.StartInfo = $StartInfo
		# Register Object Events for stdin\stdout reading
		$OutEvent = Register-ObjectEvent -InputObject $Process -EventName OutputDataReceived -Action {

		SBS_Logger $Event.SourceEventArgs.Data
		}
		$ErrEvent = Register-ObjectEvent -InputObject $Process -EventName ErrorDataReceived -Action {

		SBS_Logger $Event.SourceEventArgs.Data
		}
		# Start process
		[void]$Process.Start()
		# Begin reading stdin\stdout
		$Process.BeginOutputReadLine()
		$Process.BeginErrorReadLine()
		# Do something else while events are firing
		do
		{
			#Write-Host 'Still alive!' -ForegroundColor Green
			Start-Sleep -Seconds 1
		}
		while (!$Process.HasExited)
		# Unregister events
		$OutEvent.Name, $ErrEvent.Name |
		ForEach-Object {Unregister-Event -SourceIdentifier $_}
 }

BAT Content

@echo off
echo "hello world from a BAT file"
echo "args where %1%"
rem timeout /t 10 /nobreak > NUL
SET

===

2015-09-03 14:04:00 Task test_bat running
2015-09-03 14:04:01 "hello world from a BAT file"
2015-09-03 14:04:01 "args where greg"
2015-09-03 14:04:01 ALLUSERSPROFILE=C:\ProgramData
2015-09-03 14:04:01 APPDATA=C:\Users\build\AppData\Roaming


=====================
BAT Content

echo off
echo "hello world from a BAT file"
echo "args where %1%"
timeout /t 10 /nobreak > NUL
SET

===

2015-09-03 14:08:43 Task test_bat running
2015-09-03 14:08:54 "hello world from a BAT file"  <= 9s delay
2015-09-03 14:08:54 "args where greg"
2015-09-03 14:09:03 ALLUSERSPROFILE=C:\ProgramData <= 9s delay

The event data is not "fetched" it only exists when the event is triggered.

It is very difficult to understand what you are trying to do .  Can you ask a specific question without so much discussion. Just state what it is you need to do.

If you output the data it will list at the console. It appears you are using Write-Host. That will throw assay all data after it is displayed.

phew

I really tried, it I did too little then I would be asked for more context and examples. We are on different wavelengths

Existing examples show capturing process output

I did this and found that quirks, i.e. for each line of BAT file output, and event was not triggered

Rather it happened later that expected.

>> Is this approach wrong, and I need some ReadtoEnd() approach from the output ?

or is the issue that the cmd.exe itself is only firing output events when it thinks it should, not every line ?

Thanks

There is nothing to read.  The text is being sent to you in the event data.  The events are fired when the output of a program is available.

Change this as it will be more reliable:

		$StartInfo = New-Object System.Diagnostics.ProcessStartInfo -Property @{
			FileName = $env:comspec
			Arguments = @('F:\ScriptWork\helloworld.bat', $Label)
			UseShellExecute = $false
			RedirectStandardOutput = $true
			RedirectStandardError = $true
		}

Thanks for this tip,

I modified my test bat and its contents are below

The conclusion is although the BAT "timeout" does not affect output when run manually, it does when run from powershell.  This would suggest there isn't much we can do about this and the code is not at fault.

=====

- Running it interactively the first 3 lines are printed straight away, then 10s later the env. variables are printed, then 10s later the end

- When running the same BAT via powershell

2015-09-03 16:54:15 Task test_bat running (from powershell)
2015-09-03 16:54:36 "hello world from a BAT file"
2015-09-03 16:54:36 "args where greg"
2015-09-03 16:54:36 "I am going to sleep for 10s"
2015-09-03 16:54:46 ALLUSERSPROFILE=C:\ProgramData
....
2015-09-03 17:02:23 SystemRoot=C:\WINDOWS
2015-09-03 17:02:23 "Another 10s"
2015-09-03 17:02:23 "Done"

- Now running the same script via powershell with the pause removed

2015-09-03 17:06:02 Task test_bat running
2015-09-03 17:06:03 "hello world from a BAT file"
2015-09-03 17:06:03 "args where greg"
2015-09-03 17:06:03 ALLUSERSPROFILE=C:\ProgramData

======================

@echo off
echo "hello world from a BAT file"
echo "args where %1%"
echo "I am going to sleep for 10s"
timeout /t 10 /nobreak > NUL
SET
echo "Another 10s"
timeout /t 10 /nobreak > NUL
echo "Done"