I have the following:

if [[ "${STDOUT}" == '/dev/stdout' ]]; then
  "${mysql_cmd[@]}" <"${STDIN}" >"${STDOUT}"
else
  "${mysql_cmd[@]}" <"${STDIN}" |
    sed -e 's|[[:<:]]NULL[[:>:]]|\N|g' >"${STDOUT}"
fi

I’d like to make it into a one-liner similar to "${mysql_cmd[@]}" <"${STDIN}" | "${transformer_cmd[@]}" >"${STDOUT}".

When transformer_cmd is a “null object” (ie not the sed command), mysql must continue to be interactive. I’ve tried cat as transformer_cmd and that failed this requirement.

Is this possible? If so, how?

I’d rather avoid doing something like "${mysql_cmd[@]}" <"${STDIN}" "${transformer_cmd}" >"${STDOUT}" such that transformer_cmd includes the | but will do so if there’s no other way.