Python 2.3.4 (#2, Sep 24 2004, 08:39:09)
[GCC 3.3.4 (Debian 1:3.3.4-12)] on linux2
Type "help", "copyright", "credits" or "license" for
more information.
>>> import sys, os
>>> stdin = sys.stdin.fileno()
>>> os.read(stdin, 0)
''
>>> os.read(stdin, 0)
''
>>> os.read(stdin, -1)
asdkljasd
'asdk\x01\x00\x00\x00\x00\x00'
>>> os.read(stdin, 100)
Segmentation fault
exarkun@boson:~$

This problem persists in Python 2.4, although the
resulting incorrect behavior differs slightly (at least
on my build), as is to be expected of a memory
corrupting bug.

Note that the value returned from os.read(stdin, -1) is
incorrect in addition to the subsequent read segfaulting.