On 31/08/2023 19:31, Eric Blake wrote:
> POSIX Issue 8 will be obsoleting %b (escape sequence interpolation) so
> that future Issue 9 can change to having %b (binary literal output)
> that aligns with C2x.  But since escape interpolation may still remain
> useful, POSIX suggested %#s (which is undefined in all versions of C)
> as a possible alias for the older %b behavior.
> 
> * src/printf.c (print_formatted, usage): Support %#s as an alias
> for %b, in order to open doors to future repurposing of %b to
> binary output while still allowing access to its old behavior.
> * doc/coreutils.texi (printf invocation): Document it.
> * NEWS: Likewise.
> * tests/printf/printf-quote.sh: Add unit test coverage.

Patch looks good thanks.
I'd add in the attached test addition.

As for compat, I notice that existing coreutils will reject %#s,
while bash 5.2.15, ksh 1.0.4, dash 0.5.12 will treat as %s.

cheers,
Pádraig