From: andrew_queisser@... (andrew queisser)
Date: 2002-03-27T02:27:32+09:00
Subject: Re: File change notification?

Dale Martenson <dmartenson@multitech.com> wrote in message news:<20C86D2620F6D411A199009005DC0102F52A96@exchange_serve.multitech.prv>...
> >> Is there a straightforward way of getting notified when a file
> >> changes? In NT I can block a thread on the handle returned by
> >> FindFirstChangeNotification. Does something like this exist in Ruby?
> >> I'm currently using the Cygwin version but could be convinced to
> >> switch.
> 
> Here is a little hack that might work for you. There may be a better way,
> but I am still learning Ruby myself.
> 
> class FileCheck < Thread
>   def initialize( filename, callback, checktime=2 )
>     currentModTime = File.stat(filename).mtime
>     return super {
>       while true
>         if currentModTime < File.stat(filename).mtime then
>           callback.call
> 	  currentModTime = File.stat(filename).mtime
>         end
>         sleep(checktime)
>       end
>     }
>   end  
> end
> 
> # Do this when the file changes
> def fcAction
>   print "#{Time.now}: Something changed!!\n"
> end
> 
> # Create a file check on the passed in argument
> fc = FileCheck.new( ARGV.shift, proc { fcAction } )
> fc.run
> 
> # do something useful for a while (hopefully not this)
> while true
>   print "#{Time.now}: Nothing yet.\n"
>   sleep(3)
> end
Thanks, I was considering something like that myself buy hadn't
written anything yet. I'd like to stay away from polling, though. I
don't know enough about UNIX-style system calls to know whether
there's a built-in way of getting notified a la NT. If there is, I
suppose that it would be easy to support the same to the major Ruby
platforms.

Andrew