Tuesday, September 17, 2013

Copy files modified in the last X days with Powershell

A friend asked on the weekend for some powershell that would allow him to copy files modified in the last 7 days to a new machine. It's a great opportunity to showcase the powershell pipeline feature!
get-childitem "c:\Source" | where-object {$_.LastWriteTime -gt (get-date).AddDays(-7)} | Copy-Item -destination "C:\Target"

This one liner will work for files in a folder (it'll get messy if we recurse though, there's a fix for that coming later).

See the pipe command '|' this used to pass the output of one command as input to another command.

  1. So we get-childitem (which is the powershell name for DIR) 
  2. then we pass that to where-object with a bit of code that looks at the creationtime property. the little $_. refers to the "next object in the pipeline" so we can hook into the properties of all the obejcts we found with get-childitem, perform an evaluation on the creation time,
  3. Then the object is passed to copy-item

Now if we want to be able to recursively do this we'll need to be a little more tricksy!

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$source = "c:\users\benh\documents"
$target = "c:\test"

$files = get-childitem $source -Recurse
foreach ($file in $files)
{
    if ($file.LastWriteTime -ge (get-date).AddDays(-7))
    {
        $targetFile = $target + $file.FullName.SubString($source.Length)
        New-Item -ItemType File -Path $targetFile -Force
        Copy-Item $file.FullName -destination $targetFile
    }
}

This process uses a foreach loop which is similar to the pipeline in that it'll iterate through each item. But it allows us to use a complete script block which gives us a bit more power at the cost of performance. The main difference here is;
  1. We use an IF statement to evaluate how old the file is
  2. We figure out what the target path should be by dropping the $source directory from the files full name
  3. We create a new-item with the path we've established
  4. Then it's just copying the item as normal
Feel free to add and comments or if you've got a more elegant way of solving this problem let us know!





6 comments:

  1. Your script doesn't find files modified in the last 7 days, it finds files created in the last 7 days. Use $_.LastWriteTime to copy files modified in the last 7 days. There is a big difference.

    ReplyDelete
  2. Also use the -File option for get-childitem to only get files. e.g.

    $files = get-childitem -File $source -Recurse

    ReplyDelete
  3. Rather new to powershell and this script is working with the "Anonymous" chap's comments. However, I need the script to check whether a directory exists and if not then create a new one

    ReplyDelete
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