Unix Device File Emulation

[blaine]

On Apr 23, 11:17 am, "Ville M. Vainio" <vivai... at gmail.com> wrote:
> blaine wrote:
> > 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!
>
> Assuming you are on unix, have you considered FIFO's, os.mkfifo()?

Thank you - this is exactly what I need, I believe.  I'm having a
problem though.  The os.mkfifo() works fine, but when I read from the
file my blocking calls dont work as intended...  See below:

# Fake Nokia Screen Emulator
import sys, os

class nokia_fkscrn:
  def __init__(self, file):
    if not os.path.exists(file):
      os.mkfifo(file)
    self.fifodev = open(file, 'r')
  def read(self):
    while 1:
      r = self.fifodev.readline()
      print r

nokia = nokia_fkscrn('dev.file')
nokia.read()

This works at first, but when I write to the 'dev.file' for the first
time, the text is displayed as intended, but then the program just
keeps spitting out blank lines.  I can continue to write to the file
(using echo 'test\n' > dev.file) and this shows up in my output, but
amist a giant mass of scrolling blank lines.  This also causes my CPU
usage to shoot up to 100%.

Any ideas? This is OS X 10.4
-Blaine