A bash function to capture the stdout, stderr and return code of any line of shell into separate name-provided variables all at once without using the filesystem

capture_stdout_stderr_retcode_to_vars.bash

capture () {
  local out_var out err_var err ret_var ret debugflag
  debugflag=
  if [ "$1" = "--debug" ]; then
    debugflag=1
    shift
  fi
  if [ "$#" -lt 4 ]; then
      echo "Usage: capture [--debug] <stdoutvar> <stderrvar> <returncodevar> command [arg ...]"
      return 1
  fi
  out_var="$1"; shift
  err_var="$1"; shift
  ret_var="$1"; shift
  # just some nutso magic that captures stdout into $out, stderr into $err and return/status code into $ret
  # WITHOUT opening files, because touching the filesystem unnecessarily is bad (slows down tests, etc)
  . <({ err=$({ out=$("$@"); ret=$?; } 2>&1; declare -p out ret >&2); declare -p err; } 2>&1)
  if [ $debugflag ]; then
    echo "Command run:"
    echo "$@"
    echo "stdout:"
    echo $out
    echo "stderr:"
    echo $err
    echo "return/exit code:"
    echo $ret
  fi
  read $out_var <<<$out
  read $err_var <<<$err
  read $ret_var <<<$ret
}