(OT) python file-truncate on fc10 zero-fills file: who to ask?

[Patrick O'Callaghan]

On Thu, 2009-03-05 at 15:32 +0000, John Pilkington wrote:
> Hi:  I'm asking here because this is the most fc10-oriented list that I 
> use and I thought someone might know the answer.  I'd be happy to ask 
> elsewhere but don't know where might be the best place.
> 
> I'm trying to do shrink-to-fit with video files on fc10 after tcrequant 
> was deprecated.  vamps looks as if it will do the job but I think I need 
> to chop off a few kb from the end of the input file first to avoid a 
> failure exit.  I can do this with dd but that's slow and file truncation 
> would be better.  I can't see a command-line truncate but since I am 
> hacking the mythburn.py script I thought I had found the answer here, in 
> truncate([size]) :
> 
> http://www.python.org/doc/2.5.2/lib/bltin-file-objects.html
> 
> I've tried that.  The file size shrinks as required but the result is 
> zero-filled.  Here's some stripped-down test code:
> 
>          vobsize = os.path.getsize(source)
>          write("Initial vobsize is %s bytes" % vobsize)
> 
>          vobsize -= 2048
>          f=open(source,'wb')
>          f.truncate( vobsize )
>          f.close()
> 
>          vobsize = os.path.getsize(source)
>          write("vobsize after truncation is %s bytes" % vobsize)
> 
> Is this a known problem with python, or in its fc10 implementation? 
> Where would be the best place to ask how to do this job?

I've no idea, but I suspect you could probably write a tiny C program to
do the truncation is less time than it would take to get an answer.

poc