title: PowerShell Check file exists, update list based on response
body: <p>I'm sorry if this is considered basic but I have just started using PowerShell and I am trying to check on a filesystem whether a particular file name exists or not.  All filenames are contained within a CSV.</p>
  <p>I'd like to update the CSV with a 'true' or 'false' based on whether the directory and subfolders contains the name.   Can someone please pass over any pointers?  I am not a programmer so I am finding it difficult.</p>
  <p>Editing to add some information:</p>
  <p>The file system to search is: S:\hosted_files (and all subfolders)</p>
  <p>The CSV containing the filenames is called located in C:\Users\jroberts\Desktop\powershell and callede 'Scanned_Listing.CSV' and the filename is contained within a field called 'Image_Name' (file name contains the extension, eg .tif)</p>
  <p>Field to update on the listing would be 'Present'.</p>
  <p>If any more information is needed please let me know.</p>