Public/Copy-FileHash.ps1
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function Copy-FileHash { <# .SYNOPSIS Copies files from one location to another based on determining change via computed hash value. .DESCRIPTION The Copy-FileHash cmdlet uses the Get-FileHash cmdlet to compute the hash value of one or more files and then copies any changed and new files to the specified destination 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 copy 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 and overwrite with any changed or new files from -Path. If the folder does not exist It will be created. .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 PassThru Returns the output of the file copy as an object. By default, this cmdlet does not generate any output. .PARAMETER Recurse Indicates that this cmdlet performs a recursive copy. .PARAMETER Force Indicates that this cmdlet will copy items that cannot otherwise be changed, such as copying over a read-only file or alias. .EXAMPLE Copy-FileHash -Path C:\Some\Files -Destination D:\Some\Other\Files -Recurse Compares the files between the two trees and replaces in the destination any where they have different contents as determined via hash value comparison. #> [cmdletbinding(SupportsShouldProcess)] 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', [switch] $PassThru, [switch] $Recurse, [switch] $Force ) Begin { Try { $SourcePath = If ($PSBoundParameters.ContainsKey('LiteralPath')) { (Resolve-Path -LiteralPath $LiteralPath).Path } Else { (Resolve-Path -Path $Path).Path } If (-Not (Test-Path $Destination)) { New-Item -Path $Destination -ItemType Container | Out-Null Write-Warning "$Destination did not exist and has been created as a folder path." } $Destination = Join-Path ((Resolve-Path -Path $Destination).Path) -ChildPath '/' } Catch { Throw $_ } } Process { ForEach ($Source in $SourcePath) { $SourceFiles = (Get-ChildItem -Path $Source -Recurse:$Recurse -File).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 $Algorithm).hash } Else { #Using New-Item -Force creates an initial destination file along with any folders missing from its path. #We use (Get-Date).Ticks to give the file a random value so that it is copied even if the source file is #empty, so that if -PassThru has been used it is returned. If ($PSCmdlet.ShouldProcess($DestFile, 'New-Item')) { New-Item -Path $DestFile -Value (Get-Date).Ticks -Force -ItemType 'file' | Out-Null } $DestHash = $null } If (($SourceHash -ne $DestHash) -and $PSCmdlet.ShouldProcess($SourceFile, 'Copy-Item')) { Copy-Item -Path $SourceFile -Destination $DestFile -Force:$Force -PassThru:$PassThru } } } } } |