Next up is another parameter expansion we've already briefly seen: case modification. In this instance, case refers to lowercase and uppercase letters.
In the yes-no-optimized.sh script we originally created in Chapter 9, Error Checking and Handling, we had the following instructions:
reader@ubuntu:~/scripts/chapter_09$ cat yes-no-optimized.sh <SNIPPED>read -p "Do you like this question? " reply_variable# See if the user responded positively.if [[ ${reply_variable,,} = 'y' || ${reply_variable,,} = 'yes' ]]; then echo "Great, I worked really hard on it!" exit 0fi# Maybe the user responded negatively?if [[ ${reply_variable^^} = 'N' || ${reply_variable^^} = 'NO' ]]; then echo "You did not? But I worked so hard on it!" exit ...
