NS News & Views

By Clive Norman
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PowerShell Logging

| Tags: PowerShell Azure SysAdmin

Lately, I’ve been doing a lot of PowerShell scripting, and it’s given me the chance to expand my experience and exposure to best practices. One of the key areas I’ve focused on is logging — something that’s often overlooked but incredibly valuable when troubleshooting or reviewing script performance.

To make my life easier, I started adding a few basic functions at the top of my scripts. These functions would either log messages to a file, log to both the console and a file, or delete old log files that were over a certain age. As I implemented these functions more frequently, I realised it made sense to take this further and turn it into a reusable module.

So that’s exactly what I did. I built a PowerShell module that handles logging tasks efficiently and published it on the PowerShell Gallery. This is my first foray into submitting to the platform, and I’m pleased to be able to contribute something that may be useful to the community. Having the module available in the gallery not only streamlines my own work but also makes it easier for others who need similar logging capabilities.

If you’re interested, you can check out my module in the PowerShell Gallery (NSLoggingModule). Hopefully, it may save you time with some basic PowerShell logging!

Once the module is installed, you should have three functions available:

DeleteOldLogFiles (-days int) (-logPath string) (-scriptName string)

Deletes any log files in the log folder older than a set number of days - default is 90 days.

Log (-message string) (-logPath string) (-scriptName string)

Creates a log folder in logpath location (if doesn’t already exist) - default is local Temp directory.
Creates a log file within the log folder titled as device name, script name, and current date (e.g. computerName-scriptName-22-09-2024.log) - default script name is “-”.
Each time the function is called, a timestamped line is created within the log file, pre-pended to whatever string is passed in.

LogAndConsole (-message string) (-logPath string) (-scriptName string)

Logs to file (as above) but also writes out to the console.

(it’s worth noting that you do need to pass in the logpath (and script name if required) on each line otherwise the default will be the local Temp directory. In my example I just assign the logpath and scriptname to variables for re-use)

Script used in module


#region LOGGING

# Get the computer name
$computerName = $Env:COMPUTERNAME

#region LOGGING FUNCTIONS

# Function to create log entries
function Log {
    <#
    .SYNOPSIS
    Creates a log entry.
  
    .DESCRIPTION
    This function creates a log entry with the current date and time in universal format and appends it to the log file.
  
    .PARAMETER message
    The message to log.
 
    .PARAMETER logPath
    The path to log file. Default is Temp.
     
    .PARAMETER scriptName
    The name of the script. Default is -
  
    .EXAMPLE
    Log -message "This is a log entry." -logPath "./" -scriptName "logfile"
    #>
    param (
        [string]$message, # Message to log
        [string]$logPath = "$env:Temp\", # Log path
        [string]$scriptName = "-" # File path
    )
    
    # Set the log folder path based on the provided or default path, with a "Logs" subfolder
    $logFolder = Join-Path -Path $logPath -ChildPath "Logs"
    
    # Set the log file name based on the computer name, script name, and current date
    $logFileName = "$computerName-$scriptName-$(Get-Date -Format 'dd-MM-yy').log"

    # Check if the log folder exists, and create it if it doesn't
    if (-not (Test-Path -Path $logFolder)) {
        New-Item -Path $logFolder -ItemType Directory | Out-Null
    }
    
    # Create log entry
    $currentTime = Get-Date -Format u  # Get the current date/time in universal format
    $outputString = "[$currentTime] $message"  # Format the log entry
    $outputString | Out-File -FilePath (Join-Path -Path $logFolder -ChildPath $logFileName) -Append  # Append to log file
}

# Function to log messages to both the console and the file
function LogAndConsole {
    <#
    .SYNOPSIS
    Logs messages to both the console and the file.
  
    .DESCRIPTION
    This function logs messages to both the console with green text and to the log file.
 
    .PARAMETER message
    The message to log.
  
    .PARAMETER logPath
    The path to log file. Default is Temp.
 
    .PARAMETER scriptName
    The name of the script. Default is -
  
    .EXAMPLE
    Log -message "This is a log entry." -logPath "./" -scriptName "logfile"
    #>
    param (
        [string]$message, # Message to log
        [string]$logPath = "$env:Temp\", # Log path
        [string]$scriptName = "-" # File name
    )

    Write-Host $message -ForegroundColor Green  # Log to console
    Log -message $message -logPath $logPath -scriptName $scriptName # Log to file
}

# Function to delete old log files
function DeleteOldLogFiles {
    <#
    .SYNOPSIS
    Deletes old log files.
  
    .DESCRIPTION
    This function deletes log files older than the specified number of days.
  
    .PARAMETER Days
    The number of days after which log files will be deleted. Default is 90 days.
 
    .PARAMETER logPath
    The path to log file. Default is Temp
  
    .EXAMPLE
    DeleteOldLogFiles -Days 30 -logPath "./"
    #>
    param (
        [int]$Days = 90, # Number of days after which log files will be deleted
        [string]$logPath = "$env:Temp\", # Log path
        [string]$scriptName = "-" # File name
    )

    # Set the log folder path based on the provided or default path
    $logFolder = Join-Path -Path $logPath -ChildPath "Logs"
    $logFiles = Get-ChildItem -Path (Join-Path -Path $logFolder -ChildPath "*.log")  # Get all log files

    foreach ($file in $logFiles) {
        if ($file.LastWriteTime -le (Get-Date).AddDays(-$Days)) {
            # Delete log files older than the specified number of days
            LogAndConsole -message "[+] Deleting old log file $file..." -logPath $logPath -scriptName $scriptName
            Remove-Item -Path $file.FullName  # Remove the old log file
        }
    }
}

#endregion LOGGING FUNCTIONS

#endregion LOGGING

# Export only the public function
Export-ModuleMember -Function Log, LogAndConsole, DeleteOldLogFiles

# Example usage
#
# $p = './' (store log path as variable)
# $s = "LogFileName" (store file name as variable)
# DeleteOldLogFiles -days 30 -logpath $p -scriptName $s (named parameters example)
# LogAndConsole "HelloTwo" $p (positional parameters example)
# Log "HelloTemp" (default file and path example)