Powershell filter on a value

Question

I am trying to setup a script to copy documents from a document library to a local file share. I have found a handful of ways to do this, but I have one caveat. I need script to look at a value in a field and only copy those that match a certain value. My field is named category. How / where would I add something like "if category -eq red" to the script below to only copy files where category was "red". I am still learning Powershell and only understand the very basics at this point.

Here is a script that I found / modified from Download and delete documents using Powershell

# Add SharePoint Snapin to PowerShell            
if((Get-PSSnapin | Where {$_.Name -eq "Microsoft.SharePoint.PowerShell"}) -eq $null)     {            
  Add-PSSnapin Microsoft.SharePoint.PowerShell            
}  

$destination = "C:\\test\\"
$web = Get-SPWeb -Identity "http://TestSite/"
$list = $web.GetList("http://TestSite/testlib/")
$items = $list.Items;

function ProcessFolder {
param($folderUrl)
$folder = $web.GetFolder($folderUrl)
foreach ($file in $folder.Files) {
    #Ensure destination directory
    $destinationfolder = $destination + "/" + $folder.Url 
    if (!(Test-Path -path $destinationfolder))
    {
        $dest = New-Item $destinationfolder -type directory 
    }
    #Download file
    $binary = $file.OpenBinary() 
    $stream = New-Object System.IO.FileStream($destinationfolder + "/" + $file.Name), Create
    $writer = New-Object System.IO.BinaryWriter($stream)
    $writer.write($binary)
    $writer.Close()

}
}

#Download root files
ProcessFolder($list.RootFolder.Url)
#Download files in folders
foreach ($folder in $list.Folders) {
ProcessFolder($folder.Url)
}

I am a bit confused as to how to get access to field values as well as whether I'm supposed to pipe a where or use an if. Any help would be greatly appreciated!

Thank you very much.

Answer 1

foreach ($file in $folder.Files | ?{ $_.Item["category"] -eq 'red'  }) {

This will filter the files for ones that's underlying List Item has a category value 'red'.