The FILESYSTEM WATCHDIR method

We’ve already taken a look at the new FILESYSTEM object in a previous post, but this time we’re going to focus on a new method we’ve added called WATCHDIR.

This method allows you to monitor the contents of one or more directories on the system and be notified of any changes occurring within them.  It’s API is quite simple and takes up-to three arguments:

  1. The name of the directory to watch (required).
  2. A optional boolean flag denoting if you wish to include sub-directories. (defaults to FALSE$).
  3. An optional set of bit-flags detailing the kind of changes you are interested in.  By default WATCHDIR notifies you of file creation, changes to the name, and changes to the “Last-Write” time.

Example:

$insert msWin_FileNotify_Equates

// Only watch for files being created in the specified dir ...
watchFlags      = FILE_NOTIFY_CHANGE_CREATION$
bIncludeSubDirs = FALSE$
call exec_Method( "FILESYSTEM", "WATCHDIR", "c:\temp\incoming", |
                  bIncludeSubDirs, watchFlags )

When a change occurs the FILESYSTEM object raises a CHANGED event to notify you of the fact,  As with any other OI window or control you can write your own FILESYSTEM CHANGED event handler to respond to this – note that this event is per application, not per window.

Like the standard CHANGED event the relevant change information is passed in the “NewData” argument – in this case “NewData” contains a dynamic array with two fields:

<1> The name and path of the file being changed
<2> A code specifying the type of change

Example FILESYSTEM CHANGED event:

$insert msWin_FileNotify_Equates

changeFile = newData<1>
changeCode = newData<2>

info = ""

begin case
   case ( changeCode = FILE_ACTION_ADDED$ )
      info = "Added"
   case ( changeCode = FILE_ACTION_REMOVED$ )
      info = "Deleted"
   case ( changeCode = FILE_ACTION_MODIFIED$ )
      info = "Modified"
   case ( changeCode = FILE_ACTION_RENAMED_OLD_NAME$ )
      info = "Renamed From"
   case ( changeCode = FILE_ACTION_RENAMED_NEW_NAME$ )
      info = "Renamed To"
end case

call send_Info( info : " " : changeFile )

Technical note: The WATCHDIR method is based on the underlying ReadDirectoryChangesW Windows API function, details of which can be found here.

(Disclaimer: This article is based on preliminary information and may be subject to change in the final release version of OpenInsight 10).

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