Re: standards/60663: POSIX.1-2024: dd(1) options

["Taylor R Campbell via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR standards/60663; it has been noted by GNATS.

From: Taylor R Campbell <tcplquincy20260828%campbell.mumble.net@localhost>
To: Martin Husemann <martin%duskware.de@localhost>,
	Robert Elz <kre%munnari.OZ.AU@localhost>
Cc: gnats-bugs%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost
Subject: Re: standards/60663: POSIX.1-2024: dd(1) options
Date: Fri, 28 Aug 2026 19:13:05 +0000

 > Date: Fri, 28 Aug 2026 20:18:45 +0200
 > From: Martin Husemann <martin%duskware.de@localhost>
 >
 > You mean you could then finally do something like this?
 > 
 > 	zcat disk.img.gz | dd bs=1m iflags=fullblock of=/dev/rdk42
 > 
 > or
 > 
 > 	progress -zf disk.img.gz dd bs=1m iflags=fullblock of=/dev/rdk42
 > 
 > Sounds very usefull.
 
 For some reason I had the idea that using ibs and obs together worked
 reliably for this purpose, so I've long been doing stuff like
 
 progress -zf disk.img.gz dd ibs=64k obs=1m of=dev/rdk42
 nc ... | dd ibs=64k obs=1m of=/dev/rsd2
 
 instead of
 
 progress -zf disk.img.gz dd bs=1m of=dev/rdk42
 nc ... | dd bs=1m of=/dev/rsd2
 
 and while I noticed long ago that the bs=1m version didn't work
 reliably, the ibs=64k obs=1m version has always appeared to work for
 me.  Maybe it's an accident of coinciding with BIG_PIPE_SIZE?  Maybe
 it didn't work reliably and I just wasn't verifying hard enough?  No
 idea!
 
 Anyway, yes, having this work reliably would be useful -- I dunno why
 it took until 2024 for that to become a standard concept.