1 2unset dummyvar 3msg=`(: ${dummyvar?}) 2>&1` 4r=$? 5[ "$r" != 0 ] && case $msg in 6*dummyvar?* | *?dummyvar*) : ;; 7*) 8 printf 'Bad message: [%s]\n' "$msg" 9 exit 1 10esac 11