Hy Mike Thanks for your links, unfortunately they weren't very usefull for my specific problem.
Hy Grant Edwards Thanks for your hints. A simplified test programm to compare the function for opening a file i used ("file()") and your suggested "os.open()" showed different behaviour. My simple testprogramm: --- START --- import os msg = chr(0x02) + chr(0x36) + chr(0x00) + chr(0x01) + chr(0x0a) + chr(0xb0) + chr(0x77) f = os.open('/dev/pytest', os.O_RDWR) os.write(f,msg) os.close(f) f = file('/dev/pytest', 'wb') f.write(msg) f.close() --- END --- The "pytest" device is a very simple device-driver which prints out (using "printk()") the buffer delivered to the write function in a hexadecimal format ("Pytest write> [buffer in hex format]"). The output was: --- Start --- Pytest write> 02 36 00 01 0a b0 77 Pytest write> 02 36 00 01 0a Pytest write> b0 77 --- END --- Using os.open will work for me, i wasn't aware of the existence of several file interaces. Thanks for your help regards Aurel -- http://mail.python.org/mailman/listinfo/python-list