On Tue, 27 Jun 2023, steve jenkin wrote:

> In the mid 1980’s I worked for a small Australian outfit that did 
> “Unix”.

Neology?  Softway?

> One of the things we did was distributing software, which required 
> writing to many media.

[...]

> There was a ‘create the distro’ step of the pipeline which gathered the 
> input, followed by a loop that used ‘dd’ to block the stream into 
> media-sized parts.

Sounds like you want to put "dd" into a loop, driven by the block size and 
the media size, then using the "iseek" option on the input file to burrow 
through it.

I would use "expr" for the arithmetic because I've never bothered to
learn the Bash syntax :-)

Or have I missed something?

-- Dave