Unix Device File Emulation

Helmut Jarausch jarausch at skynet.be
Wed Apr 23 17:15:44 CEST 2008


blaine wrote:
> Hey everyone,
>   So I've got a quick query for advice.
> 
>   We have an embedded device in which we are displaying to an LCD
> device that sits at /dev/screen.  This device is not readily available
> all the time, so I am needing to write an emulator.  This will
> basically just monitor a file, /dev/screen for example, and write the
> commands to a TK or WxWindows canvas.
> 
> So sending 'line 0 0 10 10' will draw a line on my canvas from (0,0)
> to (10,10).
> 
> My question: Whats the best way to set up a monitor (in python) of
> this file? Would I simply open up the file for read, check for
> changes, get any updated data, and clear the file? Or is there some
> standard way of doing something like this that guarantees no overlap
> or data loss?
> 
> example usage: echo 'line 0 0 10 10' > /dev/screen
> 
> On the actual embedded device this is handled by a kernel module.  We
> can spit commands into it as fast as we can and the kernel module can
> keep up.  This is typical unix device file behavior.
> 
> Any suggestions or advice would be splendid.  Thanks!
> Blaine

It looks as if you need something like the Unix 'tail -f' command.
Perhaps here is some help

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/414771
http://mail.python.org/pipermail/python-list/2002-August/157510.html
http://pyinotify.sourceforge.net/


-- 
Helmut Jarausch

Lehrstuhl fuer Numerische Mathematik
RWTH - Aachen University
D 52056 Aachen, Germany



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