Powershell script to copy only files that already exist in target folder

Question

I have a folder full of files, let's call it folder A, some of which (but not all) are also present in another folder, called folder B.

The files in B are out of date, and I would like to copy the newer versions of those files from A to B (overwrite the ones in B), but not copy all of the extra files from A which do not already exist in B.

There may also be files in B that are not in A.

Is there a way to do this with powershell? I know I can probably do it with xcopy, as in this question but I am looking for a pure Powershell solution.

I do not care if the files are newer, older or unchanged etc.

Answer 1

This is relatively straightforward by looping through the files in A and checking if they're in B.

$aDir = "C:\Temp\powershell\a"
$bDir = "C:\Temp\powershell\b"

$aFiles = Get-ChildItem -Path "$aDir"
ForEach ($file in $aFiles) {
    if(Test-Path $bDir\$file) {
        Write-Output "$file exists in $bDir. Copying."
        Copy-Item $aDir\$file $bDir
    } else {
        Write-Output "$file does not exist in $bDir."
    }
}