popen3 stdin problem

[Nicolai Ehemann]

I have a strange problem using popen3() on a linux machine with python
2.1.1:
I use

  inf, outf, erff os.popen3("cmd ....")

to start a process which makes a lot of output to stdout and awaits
user input on stdin. Capturing the output with outf.readline() works
perfectly, but as far as I can see sending input to the process via
inf.write("command") or inf.write("command\n") does not get through to
the child process. When called interactively, cmd reacts to input from
stdin with some status output, and there is a /QUIT-Command which
should stop the program. Nothing of this happens (outf.readline()
never gets EOF).

Any ideas what the problem could be?

Nico