function Get-DatastoreDir ($DSName){

  $dsImpl = Get-Datastore -Name $DSName
  $ds = Get-Datastore -Name $DSName | Get-View
  $dsBrowser = Get-View -Id $ds.Browser

  $datastorepath = "[http://" + $ds.Summary.Name + "|http://" + $ds.Summary.Name + "]"
  
  $searchspec = New-Object VMware.Vim.HostDatastoreBrowserSearchSpec
  $searchSpec.matchpattern = "*"
  $searchSpec.details = New-Object VMware.Vim.FileQueryFlags
  $searchSpec.details.fileSize = $true
  $searchSpec.details.fileType = $true
  $searchSpec.details.modification = $true
 
  $taskMoRef = $dsBrowser.SearchDatastoreSubFolders_Task($datastorePath, $searchSpec) 
  $task = Get-View $taskMoRef 
  while ($task.Info.State -eq "running"){$task = Get-View $taskMoRef}

  $report = @() 
  foreach ($result in $task.info.Result){
    foreach($file in $result.File){
      if($file.GetType().Name -ne "FolderFileInfo"){
	    $row = "" | Select Filename, Folder, Filesize, Modification
        $row.Filename = $file.Path
	    $row.Folder = $result.FolderPath
	    $row.Filesize = $file.FileSize
	    $row.Modification = $file.Modification
	    $report += $row
	  }
    }
  }
  $report
}

Get-DatastoreDir <datastore-name> | Where-Object {$_.Filename -match "flat"}

Get-Datastore | %{Get-DatastoreDir $_.Name} | Where-Object {$_.Filename -match "flat"}