function-logging-example.ps1

#----------------------------------------------------------[Declarations]----------------------------------------------------------
# function Write-Log
[string] $strLogfilePath = "C:\Temp"
[string] $strLogfileDate = Get-Date -Format "yyyy-MM-dd_HH-mm-ss"
[string] $strLogfileNamePrefix = "Log_"
[string] $strLogfileName = $($strLogfileNamePrefix + $strLogfileDate + ".log")
[string] $strLogfile = $strLogfilePath + "\" + $strLogfileName

#-----------------------------------------------------------[Functions]------------------------------------------------------------

function Write-Log {
    [CmdletBinding()]
    param (
        [Parameter(
            Mandatory=$true,
            Position=0)]
        [ValidateNotNullOrEmpty()]
        [string] $LogText = "",

        [Parameter(
            Mandatory=$true,
            Position=1)]
        [ValidateNotNullOrEmpty()]
        [ValidateSet('Info','Success','Warning','Error')]
        [string] $LogStatus= "Info",

        [Parameter(Mandatory=$false)]
        [switch] $Absatz,

        [Parameter(Mandatory=$false)]
        [switch] $EventLog
    )

	[string] $strLogdate = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    [string] $strTextColor = "White"
    [string] $strLogFileAbsatz = ""
    [string] $strLogFileHeader = ""

    if ( -not (Test-Path $strLogfilePath) ) {
        Write-Host "Der angegebene Pfad $strLogfilePath existiert nicht!" -ForegroundColor Red
        exit
    }

    # Add a header to logfile, if the logfile not exist
    If ( -not (Test-Path $strLogfile) ) {
        $strLogFileHeader = "$("#" * 120)`n"
        $strLogFileHeader += "{0,-21} {1,0}" -f "# Skript:", "$($MyInvocation.ScriptName)`n"
        $strLogFileHeader += "{0,-21} {1,0}" -f "# Startzeit:", "$(Get-Date -Format "dd.MM.yyyy HH:mm:ss")`n"
        $strLogFileHeader += "{0,-21} {1,0}" -f "# Startzeit:", "$(Get-Date -Format "dd.MM.yyyy HH:mm:ss")`n"
        $strLogFileHeader += "{0,-21} {1,0}" -f "# Ausführendes Konto:", "$([Security.Principal.WindowsIdentity]::GetCurrent().Name)`n"
        $strLogFileHeader += "{0,-21} {1,0}" -f "# Computername:", "$env:COMPUTERNAME`n"
        $strLogFileHeader += "$("#" * 120)`n"

        Write-Host $strLogFileHeader
        Add-Content -Path $strLogfile -Value $strLogFileHeader -Encoding UTF8
    }
   

    switch($LogStatus) {
        Info {
            $strTextColor = "White"
        }
        Success {
            $strTextColor = "Green"
        }
        Warning {
            $strTextColor = "Yellow"
        }
        Error {
            $strTextColor = "Red"
        }
    }

    # Add an Absatz if the parameter is True
    if($Absatz) {
        [string] $strLogFileAbsatz = "`r`n"
    }

    #Format the text output
    $LogText = "{0,-20} - {1,-7} - {2,0}" -f "$strLogdate", "$LogStatus", "$LogText $strLogFileAbsatz"

    # Write output to powershell console
    Write-Host $LogText -ForegroundColor $strTextColor

    # Write output to logfile
    Add-Content -Path $strLogfile -Value $LogText -Encoding UTF8

    # Add Logfile to local Eventlog of the operating system 
    if($EventLog) {
        Write-EventLog -LogName 'Windows PowerShell' -Source "Powershell" -EventId 0 -Category 0 -EntryType $LogStatus -Message $LogText
    }

}

#-----------------------------------------------------------[Execution]------------------------------------------------------------

Write-Log -LogText "Das ist ein Test." -LogStatus Info
Write-Log -LogText "Das ist ein Test." -LogStatus Success
Write-Log -LogText "Das ist ein Test." -LogStatus Warning
Write-Log -LogText "Das ist ein Test." -LogStatus Error -Absatz
Write-Log -LogText "Das ist ein Test." -LogStatus Error -EventLog