Powershell logging from invoke-command

Question

I have a script that includes a function for logging. The function writes log to $msg variable then writes the message to the screen. i can redirect this output to a .txt file for logging.

I need to run the script to multiple servers using invoke-command and write the log output to a txt file on the computer running the script.

I am trying to figure out how to output $msg in the write-log function from the PSSession and return it so I can create a master log file for all the servers. Should I create and populate a custom object? Not sure how to do that and get the results back from the remote session.

Can this even be done?

Here is an example of the code I am using and what the log file output should look like:

$servers = 'Server1','Server2'
$logfile = 'c:\scripts\logs\Reg-DLL-log.txt'

foreach($server in $servers){
    invoke-command -cn $server -sb{
        Param($server)

        Function write-log{
            [cmdletbinding()]
            Param(
                [Parameter(ValueFromPipeline=$true,Mandatory=$true)] [ValidateNotNullOrEmpty()]
                [string] $Message,
                [Parameter()] [ValidateSet(“Error”, “Warn”, “Info”)]
                [string] $Level = “Info”,
                [Parameter()] [ValidateRange(1,30)]
                [Int16] $Indent = 0
            )
            $msg = "{0} {1}{2}:{3}" -f (Get-Date -Format "yyyy-MM-dd HH:mm:ss"), $Level.ToUpper(), (" " * $Indent), $Message
                #This is output to screen
                switch ($Level) {
                    'Error' { Write-Host ('{0}{1}' -f (" " * $Indent), $Message) -ForegroundColor 'Red'}
                    'Warn' { Write-Host ('{0}{1}' -f (" " * $Indent), $Message) -ForegroundColor 'Yellow'}
                    'Info' { Write-Host ('{0}{1}' -f (" " * $Indent), $Message) -ForegroundColor 'white'}
        }}

        write-log -message 'Begin DLL registration for $server' -level Info
        $RegFile = "cimwin32.dll"
        regsvr32 $RegFile /s
        write-log -message 'registered $RegFile' -level Info
        write-log -message 'End DLL registration for $server' -level Info

    } -ArgumentList $server
}

Log output to Reg-DLL-log.txt should look like this:

2013-06-19 11:25:12 INFO:Begin DLL registration for Server1
2013-06-19 11:25:12 INFO:registered cimwin32.dll
2013-06-19 11:25:12 INFO:End DLL registration for Server1
2013-06-19 11:25:12 INFO:Begin DLL registration for Server2
2013-06-19 11:25:12 INFO:registered cimwin32.dll
2013-06-19 11:25:12 INFO:End DLL registration for Server2

Answer 1

As documented, Invoke-Command returns all command output, so you could use Write-Output instead of Write-Host and pipe the returned output into a file. There's no fancy coloring with Write-Output, though. You could, however, write 'Info', 'Warn' and 'Error' level messages to the correct streams using Write-Output, Write-Warning and Write-Error. Also, you may want to suppress output from regsvr32.

foreach ($server in $servers) {
  Invoke-Command -Computer $server -ScriptBlock {
    Param($server)

    Function write-log {
      ...
      switch ($Level) {
        'Error' { Write-Error $msg }
        'Warn'  { Write-Warning $msg }
        'Info'  { Write-Output $msg }
      }
    }

    write-log -message 'Begin DLL registration for $server' -level Info
    $RegFile = "cimwin32.dll"
    regsvr32 $RegFile /s | Out-Null
    write-log -message 'registered $RegFile' -level Info
    write-log -message 'End DLL registration for $server' -level Info
  } -ArgumentList $server | Out-File -Append $masterLog
}