Subject: Bug#859021: dd: document that bs overrides ibs and obs

From: Pádraig Brady <[email-masked]>
Date: Wed, 29 Mar 2017 19:06:46 -0700

On 29/03/17 09:04, Chris Davies wrote:
> Package: coreutils
> Version: 8.25-2+b1
> Severity: minor
> 
> Dear Maintainer,
> 
> The man page for dd does not define an interaction between bs and its more
> specific ibs and obs options. POSIX does mandate that bs, if specified,
> shall override ibs and obs. Empirically I have determined that coreutils
> dd implements POSIX behaviour, so I should like to suggest the man page
> is updated to state that bs overrides ibs and/or obs.
> 
> 
> POSIX man page at http://www.unix.com/man-page/posix/1posix/dd/ defines
> the three options bs, ibs, and obs as follows:
> 
>     ibs=expr
> 	Specify the input block size, in bytes, by expr (default is 512).
> 
>     obs=expr
> 	Specify the output block size, in bytes, by expr (default is 512).
> 
>     bs=expr
> 	Set  both input and output block sizes to expr bytes, superseding
> 	ibs= and obs=. If no conversion other than sync, noerror, and
> 	notrunc is specified, each input  block shall be copied to the
> 	output as a single block without aggregating short blocks.
> 
> 
> Extracts from the current coreutils man page read as follows:
> 
>     bs=BYTES
> 	read and write up to BYTES bytes at a time
> 
>     ibs=BYTES
> 	read up to BYTES bytes at a time (default: 512)
> 
>     obs=BYTES
> 	write BYTES bytes at a time (default: 512)
> 
> 
> I would like to suggest that the explanation is amended as follows:
> 
>     bs=BYTES
> 	read and write up to BYTES bytes at a time (default:
> 	512); overrides ibs and obs

Done in your name upstream at:
http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=v8.27-15-gc1c558e