#!/bin/bash

{
  IFS=$'\n' read -r -d '' CAPTURED_STDERR
  IFS=$'\n' read -r -d '' CAPTURED_STDOUT
} < <((printf '\0%s\0' "$(./useless.sh)" 1>&2) 2>&1)

echo 'Here is the captured stdout:'
echo "${CAPTURED_STDOUT}"
echo

echo 'And here is the captured stderr:'
echo "${CAPTURED_STDERR}"
echo

# function launch {
#   echo START
#   bash -c "set -TEue -o pipefail; . ./useless.sh"
#   echo END
# }
#
# set -TEue -o pipefail
# stderr=$(launch 3>&1 1>&2 2>&3 | tee /dev/stderr)
# >&2 echo "ERR: $stderr"
# # (
#   echo -n "ERR: "
#   cat stderr
# ) >&2
# >&2 echo 'here is the captured stderr:'
# >&2 echo "$(<stderr)"
# >&2 echo