Get STDOUT and STDERR in Separate Variables

Get STDOUT and STDERR in Separate Variables.sh

#! /usr/bin/env bash

foo() {
  echo "STDOUT contents (called with args $*)"
  echo "STDERR contents (called with args $*)" >&2
  return 42
}

printOutBothStdoutAndStderrSeparately() {
  echo "$({

    error="$(
      { output="$( "$@" )"; } 2>&1;
      ret=$?
      declare -p output >&2
      exit $?
    )"

    ret=$?

    declare -p error

  } 2>&1 )"
}

printOutBothStdoutAndStderrSeparately foo hello world

# Output:
# declare -- output="STDOUT contents (called with args hello world)"
# declare -- error="STDERR contents (called with args hello world)"