Public/Compare-FileHash.ps1
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function Compare-FileHash { <# .SYNOPSIS Compares files from one location to another based on determining change via computed hash value. .DESCRIPTION The Compare-FileHash cmdlet uses the Get-FileHash cmdlet to compute the hash value of one or more files and then returns any changed and new files from the specified source path. If you use the -Recurse parameter the cmdlet will synchronise a full directory tree, preserving the structure and creating any missing directories in the destination path as required. The purpose of this cmdlet is to compare specific file changes between two paths in situations where you cannot rely on the modified date of the files to determine if a file has changed. This can occur in situations where file modified dates have been changed, such as when cloning a set of files from a source control system. .PARAMETER Path The path to the source file/s or folder/s to copy any new or changed files from. .PARAMETER LiteralPath The literal path to the source file/s or folder/s to copy any new or changed files from. Unlike the Path parameter, the value of LiteralPath is used exactly as it is typed. No characters are interpreted as wildcards. .PARAMETER Destination The Destination folder to compare to -Path or -LiteralPath and return any changed or new files. .PARAMETER Algorithm Specifies the cryptographic hash function to use for computing the hash value of the contents of the specified file. A cryptographic hash function includes the property that it is not possible to find two distinct inputs that generate the same hash values. Hash functions are commonly used with digital signatures and for data integrity. The acceptable values for this parameter are: SHA1 | SHA256 | SHA384 | SHA512 | MACTripleDES | MD5 | RIPEMD160 If no value is specified, or if the parameter is omitted, the default value is SHA256. .PARAMETER Exclude Exclude one or more files from being compared. .PARAMETER Recurse Indicates that this cmdlet performs a recursive comparison. .EXAMPLE Compare-FileHash -Path C:\Some\Files -Destination D:\Some\Other\Files -Recurse Compares the files between the two trees and returns any where they have different contents as determined via hash value comparison. #> [cmdletbinding()] param( [Parameter(Mandatory, ValueFromPipeline, ValueFromPipelineByPropertyName, ParameterSetName = 'Path')] [ValidateScript( {if (Test-Path $_) {$True} Else { Throw '-Path must be a valid path.'} })] [String[]] $Path, [Parameter(Mandatory, ValueFromPipelineByPropertyName, ParameterSetName = 'LiteralPath')] [ValidateScript( {if (Test-Path $_) {$True} Else { Throw '-LiteralPath must be a valid path.'} })] [String[]] $LiteralPath, [Parameter(Mandatory)] [ValidateScript( {if (Test-Path $_ -PathType Container -IsValid) {$True} Else { Throw '-Destination must be a valid path.' } })] [String] $Destination, [ValidateSet('SHA1', 'SHA256', 'SHA384', 'SHA512', 'MACTripleDES', 'MD5', 'RIPEMD160')] [String] $Algorithm = 'SHA256', [string[]] $Exclude, [switch] $Recurse ) begin { try { $SourcePath = if ($PSBoundParameters.ContainsKey('LiteralPath')) { (Resolve-Path -LiteralPath $LiteralPath).Path } else { (Resolve-Path -Path $Path).Path } if (-Not (Test-Path $Destination)) { throw "$Destination does not exist" } else { $Destination = Join-Path ((Resolve-Path -Path $Destination).Path) -ChildPath '/' } } catch { throw $_ } } process { foreach ($Source in $SourcePath) { $SourceFiles = (Get-ChildItem -Path $Source -Recurse:$Recurse -File -Exclude $Exclude).FullName foreach ($SourceFile in $SourceFiles) { $DestFile = Get-DestinationFilePath -File $SourceFile -Source $Source -Destination $Destination $SourceHash = (Get-FileHash $SourceFile -Algorithm $Algorithm).hash if (Test-Path $DestFile) { $DestHash = (Get-FileHash $DestFile -Algorithm $Algorithm).hash } else { Write-Verbose "New file: $SourceFile" $DestHash = $null } if ($SourceHash -ne $DestHash) { Get-ChildItem -Path $SourceFile } } } } } |