If anyone who has read this thread is still unclear on what this has to do with flock, the answer is "nothing", though it's an understandable confusion. File locking via flock is advisory. Programs can cheerfully choice to ignore it (or, more likely, can fail out of ignorance to adhere to the advisory locking protocol). Yes, flock doesn't work on Win9x/WinME, but that, as clintp points out above is a separate issue.