I noticed that the BASH and Korn printf
built-ins output ESC with printf '\e' but
the DAsh printf outputs the actual characters.

With printf '%b' '\e' BASH outputs ESC, while
Korn and DAsh output the characters.

I had a look into POSIX. I'm not sure I've
managed to locate all the relevant sections
but those I've read do not mention \e as an
escape sequence which means that using it is
unspecified behaviour. If I'm right then
which are the allowed behaviours ?