[Python-Dev] PEP 389: argparse - new command line parsing module

Jon Ribbens jon+python-dev at unequivocal.co.uk
Thu Oct 1 12:39:38 CEST 2009

On Thu, Oct 01, 2009 at 09:58:59AM +0100, Paul Moore wrote:
> (Question - is it *ever* possible for a Unix program to have invalid
> file descriptors 0,1 and 2? At startup - I'm assuming anyone who does
> os.close(1) knows what they are doing!)

Yes, at startup you just have the file descriptors your parent process
gave you. This may or may not include 0, 1, and 2, and may or may not
include other descriptors too.

I seem to recall there have been security holes caused in the past by
people assuming 0-2 will exist.

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