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Powershell Copy-Item but only copy changed files

Asked 2009-03-24T15:00:38.813
33

I am trying to recurse through a directory and copy it from A to B. That can be done with the following:

Copy-Item C:\MyTest C:\MyTest2 –recurse

I want to be able though to only copy new files (ones that exist in src but not dest) and also only copy files that may have changed based off a CRC check and not a datetime stamp.

$file = "c:\scripts"
param
(
$file
)

$algo = [System.Security.Cryptography.HashAlgorithm]::Create("MD5")
$stream = New-Object System.IO.FileStream($file, [System.IO.FileMode]::Open)

$md5StringBuilder = New-Object System.Text.StringBuilder
$algo.ComputeHash($stream) | `
% { [void] $md5StringBuilder.Append($_.ToString("x2")) }
$md5StringBuilder.ToString()

$stream.Dispose()

This code gives me a CRC check on a specific file...I am just not sure how to put the two scripts together to really give me what I need. I also don't know if the CRC check above is actually the correct way of doing this.

Does anyone have any insight?

powershell xcopy copy-item
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1 Answer

10

Here is some of the guidelines how you can your script to be more maintainable.

Conver the original script as a filter.

filter HasChanged { 
    param($file)

    # if $file's MD5 has does not exist
    # then return $_
}

Then simply filter all files that are updated and copy them.

# Note that "Copy-Item" here does not preserve original directory structure
# Every updated file gets copied right under "C:\MyTest2"
ls C:\MyTest -Recurse | HasChanged | Copy-Item -Path {$_} C:\MyTest2

Or you can create another function that generates sub directory 

ls C:\MyTest -Recurse | HasChanged | % { Copy-Item $_ GenerateSubDirectory(...) }
answered 2009-03-24T16:18:46.597

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