The most voted answer will work in most cases. But since I use set +o errexit in bash it errored out. This should work better in bash:
fail_if_stderr() ( # save current options bash_options="${-}" # disable exit on error set +o errexit # Save return code of command in rc rc=$({ ("$@" 2>&1 >&3 3>&- 4>&-; echo "$?" >&4) | grep '^'>&2 3>&- 4>&- } 4>&1) # Save return code of grep in err_in_stderr err_in_stderr=$? # enable exit on error if it was previously enabled test "${bash_options#*e*}" != "$bash_options" && set -o errexit # exit with original return code if it's not zero [ "$rc" -eq 0 ] || exit "$rc" # exit with return code 125 if something was in stderr [ "$err_in_stderr" -ne 0 ] || exit 125) 3>&1