#!/bin/bash tty if [[ $? -ne 0 ]] ; then # command returned nonzero echo "not a tty" else # command returned zero n=$? ((n=$

#!/bin/bash tty if [[ $? -ne 0 ]] ; then # command returned nonzero echo "not a tty" else # command returned zero n=$? ((n=$n+2)) ((n=$n+2)) echo "0+2+2=$n"; fi