Answer:
The code is given as below: The input and output is as given for one case.
Explanation:
echo -e "Enter A, B or C : \c" #Printing the line on the screen
read -rN 1 test #read the character in the variable test
echo
case $test in #Setting up the case structure for variable test
[[:lower:]] ) #checking all lower case letters
echo You did not enter A, B or C;;
[D-Z] ) #checking upper case letters from D to Z
echo You did not enter A, B or C;;
A ) #Condition to check A
echo You entered A;;
B ) #Condition to check B
echo You entered B;;
C ) #Condition to check C
echo You entered C;;
esac #Exiting the case structure
