Just use tr command to transform lowercase letters into uppercase as: tr a-z A-Z < file.txt #transforms letters into uppercase in a file echo 'HELLO' | tr A-Z a-z #Outputs: 'hello'
echo "enter a char" read c if [[ $c == [A-Z] ]]; then echo "upper" elif [[ $c == [a-z] ]]; then echo "lower" else echo "Digit or special symbols!" fi
