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May 25

old Unix checksum algorithm

I just brought this up at Talk:BSD checksum, but I doubt it'll get much attention there. I believe that the non-SysV algorithm implemented by the Unix/Linux sum(1) program goes all the way back to the earliest versions of Unix, V7 and perhaps earlier. So I believe that calling it the "BSD" checksum algorithm is rather misleading and wrong. Does anyone know how far back the algorithm really goes? I was tempted to propose renaming the article to "V7 checksum", but that might be almost as misleading if the same code was around in V6 and before.

I'm pretty sure the V7 sources are online somewhere, which would be one good data point for this question. —Steve Summit (talk) 22:02, 25 May 2016 (UTC)[reply]

V7 source at http://minnie.tuhs.org/cgi-bin/utree.pl?file=V7/usr/src/cmd/sum.c -- Finlay McWalter··–·Talk 22:31, 25 May 2016 (UTC)[reply]

Cool! That looks the same, and it compiles (even today) with only one warning, and... generates exactly the same results. Good. Thanks. —Steve Summit (talk) 23:03, 25 May 2016 (UTC)[reply]

V5 has an asm file which may be use same algorithm - http://minnie.tuhs.org/cgi-bin/utree.pl?file=V5/usr/source/s2/sum.s -- Finlay McWalter··–·Talk 22:37, 25 May 2016 (UTC)[reply]

Version five! My, oh, my. And it's in assembler. Whouda thunk. Perhaps I'll try booting up my old PDP-11 tonight and trying it out. —Steve Summit (talk) 23:03, 25 May 2016 (UTC)[reply]

The same site has earlier versions, but I haven't looked to see if they have a sum.s or the like. This guy has an in-browser PDP-11 emulator, which at least runs V6; I daresay you run run as on the earlier sum.s versions inside that. -- Finlay McWalter··–·Talk 23:07, 25 May 2016 (UTC)[reply]

HTTP proxy for fixing bad RSS feeds?

The news reader I use has a problem with some RSS feeds that I want to read. I think those feeds have XML issues. Is there a simple to use HTTP proxy that will allow me to fix the issues using a custom script? Such a tool can come handy in other situations. Suggestions? --134.242.92.97 (talk) 22:40, 25 May 2016 (UTC)[reply]