How to compare files under 2 folders with PowerShell;

Question

I am a newbie in PowerShell, and trying to learn the things from few forums and msdn. Now i got some requirement from my group of learners.

I am trying to compare 2 folder's files with each other in powershell, for effective file comparison i am using MD5 Hashes. Till now i have created a code like this,

[Cmdletbinding()]
Param
(
[Parameter(Position=0, Mandatory)][ValidateScript({ Test-Path -Path $_ })][string]$SourceFolder,
[Parameter(Position=1, Mandatory)][ValidateScript({ Test-Path -Path $_ })][string]$DestinationFolder
) 
$SourceFolderList =@()
$DestinationFolderList =@()

$Sourcefiles = @(Get-ChildItem -Path $SourceFolder -Filter *.log)
foreach($srcFile in $Sourcefiles )
{
    $SourceFolderHash = [ordered]@{}
    $SourceFolderHash.Name = $srcFile.Name
    $SourceFolderHash.FullName = $srcFile.FullName
    $obj = New-Object PSObject -Property $SourceFolderHash
    $SourceFolderList+= $obj
}

$Destfiles = @(Get-ChildItem -Path $DestinationFolder -Filter *.log)
foreach($Destfile in $Destfiles )
{
    $DestinationFolderHash = [ordered]@{}
    $DestinationFolderHash.Name = $Destfile.Name
    $DestinationFolderHash.FullName = $Destfile.FullName
    $obj = New-Object PSObject -Property $DestinationFolderHash
    $DestinationFolderList+= $obj
}

$SourceFolderList =@() & $DestinationFolderList =@() are Arrays with Name & FullName properties.

Now i am trying to create a new array with values which matches in the $SourceFolderList & $DestinationFolderList ( I hope i am going in the right way?!)

But the problem is, i am not sure how to loop through each item in the Arrays and get the fullnames of each file from 2 folders to pass as params to MD5hash Function.

I am trying in this way

##1
For ($i =$j=0; $i -le $SourceFolderList.Count -and $j -le $DestinationFolderList.Count; $i++ -and $j++)
 {
    $file1Name = $SourceFolderList[$i].Name 
    $file1Path = $SourceFolderList[$i].FullName 

    $file2Name = $DestinationFolderList[$j].Name 
    $file2Path = $DestinationFolderList[$j].FullName  
 }

##2
foreach( $file in $SourceFolderList)
{
    if($DestinationFolderList.Name  -contains $file.Name )
    {
        Write-Host  $file.Name -ForegroundColor Cyan 
        Write-Host  $DestinationFolderList.($file.Name).FullName -ForegroundColor Yellow
    }
}

In the 1st way i am not getting correct File Paths << Index is mismatching for Destination folder's file paths >>

In the 2nd Way i am not at all getting the Full Path of file.

Please correct me if am going in the wrong way to achieve my requirement. And please help me to solve this issue.

Answer 1

I think your're making your task more difficult that it is, by gathering file info into the arrays. Why don't you just iterate over the files in the source folder and compare their hashes with hashes of files in the destination folder on the fly:

function Compare-Folders
{
    [CmdletBinding()]
    Param
    (
        [Parameter(Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true)]
        [string]$Source,

        [Parameter(Mandatory = $true, ValueFromPipelineByPropertyName = $true)]
        [string]$Destinaton,

        [Parameter(ValueFromPipelineByPropertyName = $true)]
        [string]$Filter
    )

    Process
    {
        # Iterate over files in source folder, skip folders
        Get-ChildItem -Path $Source -Filter $Filter | Where-Object {!$_.PsIsContainer} | ForEach-Object {
            # Generate file name in destination folder
            $DstFileName = Resolve-Path -Path (Join-Path -Path $Destinaton -ChildPath (Split-Path -Path $_.FullName -Leaf))

            # Create hashtable with filenames and hashes
            $Result = @{
                SourceFile = $_.FullName
                SourceFileHash = (Get-FileHash -Path $_.FullName -Algorithm MD5).Hash
                DestinationFile = $DstFileName
                DestinationFileHash = (Get-FileHash -Path $DstFileName -Algorithm MD5).Hash
            }

            # Check if file hashes are equal and add result to hashtable
            $Result.Add('IsEqual', ($Result.SourceFileHash -eq $Result.DestinationFileHash))

            # Output PsObject from hashtable
            New-Object -TypeName psobject -Property $Result |
                Select-Object -Property SourceFile, SourceFileHash , DestinationFile, DestinationFileHash, IsEqual
        }
    }
}