Merge-CSVFiles: PowerShell Function to Merge a Folder of CSVs and Append a Filename column

Merge-CSVFiles.ps1

# Usage: Merge-CSVFiles 
# Usage: Merge-CSVFiles -Path C:\files\to\merge\ -Filter "*.csv" -OutputFile C:\Temp\merged.csv
# Combination of https://declanbright.com/downloads/Combine-Files.ps1 and https://gallery.technet.microsoft.com/scriptcenter/CombineMerge-multiple-CSV-23a53e83

function Merge-CSVFiles { 
[cmdletbinding()] 
param( 
    [string]$Path = ".",
	  [string]$Filter = "*.csv",
    [string]$OutputFile = "c:\Temp\Merged_$(get-date -f yyyy-MM-dd_HHmmss).csv"
) 

if (!(Test-Path -path $Path)) {
    Write-Host "`n`n  ERROR: Path ""$Path"" is invalid`n"
    break
}

$Files = Get-ChildItem $Path -filter $Filter

$Output = @(); 
foreach($CSV in $Files) { 
	$fullpath = $Path + $CSV
	Write-Host $fullpath
    if(Test-Path $fullpath) { 
        $FileName = [System.IO.Path]::GetFileName($fullpath) 
        $temp = Import-CSV -Path $fullpath | select *, @{Expression={$FileName};Label="FileName" } 
        $Output += $temp 
 
    } else { 
        Write-Warning "$fullpath : No such file found" 
    } 
 
} 
$Output | Export-Csv -Path $OutputFile -NoTypeInformation 
Write-Output "$OutputFile successfully created" 
 
}