Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!hplabs!hpcc01!gph
From: gph@hpcc01.HP.COM (Paul Houtz)
Newsgroups: comp.unix.questions
Subject: Re: Problems with diff -e and ed?
Message-ID: <10910002@hpcc01.HP.COM>
Date: 28 Mar 90 16:36:24 GMT
References: <10910001@hpcc01.HP.COM>
Organization: HP Corporate Computing Center
Lines: 37

I wrote:

>Does anyone know what types of problems are associated with using
>diff -e  and then storing the result and the original and using it as
>backup file, using ed to restore the original.
>
>I know that a file with a line with a single . in it will confuse ed, and
>I have taken care of that.   Is there anything else?
>
>Thanks!
>
>gph@hpsdesis.HP.COM
----------

   Ooops, I guess I wasn't clear in my original question. I know that if 
   the file changes underneath the delta, one will have problems.

   Let me clarify my question:

   I would like to use this as a method of transmitting only changes to a
   file over a network, rather than the entire file.   I have other methods
   (checksum, datecodes, etc) that will make absolutely certain that the
   changes generated by diff -e will be applied to EXACTLY the same file.

   What I want to know is, has anyone heard of anything that could cause
   diff -e to produce output that is not correctly applied by ed?
   Are there any other characters or sequences of characters like the 
   single dot mentioned above that can blow up diff -e or ed?   Are these
   programs limited by record size or file size?

      For example, I heard that someone had problems with a linelength
      of 124 with a "\" character followed by a number of tabs.  I have
      not been able to reproduce this problem.

   Thanks again!

   gph@hpsdesis.HP.COM