Need help with error correction.

[Greg Hunt]

In article <steve.665748651 at paddy>, steve at gapos.bt.co.uk (Steve Rooke) writes:
> I have two sites, one sending a file, the other receiving.  There is a lot
> of corruption at the receiving end caused by line noise.  I am not able to
> use any standard form of error correction on the line but I can request
> retransmission of the file, as many times as needed, over another link.
> 
> I need to be able to compair these files and reconstruct the original with
> reasonable confidence.  By that I mean that if two, or more, files have the
> same text at a certain point then I am reasonably confident that the text
> is OK.
> 
> Has anyone tried to do this sort of thing before and how did you do it,
> please?  Solutions based upon diff would do, I guess, for a majority of
> the time.

When I've had file transmission problems, I've used sum(1) to produce
a checksum of the file on both the sending side machine and the
receiving side machine and compared the results.  If they weren't the
same, then I knew that something got corrupted in the transmission and
I got the file again.

If the systems you're working with have sum(1) that might be an easy
thing to use.  Also, sum(1) will work for any sort of file, it doesn't
just have to be text (which is the only thing diff(1) can look at).

-- 
Greg Hunt                        Internet: hunt at dg-rtp.rtp.dg.com
DG/UX Kernel Development         UUCP:     {world}!mcnc!rti!dg-rtp!hunt
Data General Corporation
Research Triangle Park, NC, USA  These opinions are mine, not DG's.