Case Statement Nested in While Loop causes Infinite Loop in BASH Script

Question

I'm trying to make this BASH script require the user to input a value between 1 through 4 to choose a ninja turtle in the case statement. Any other value will cause $COUNTER to remain equal to 0 therefore requiring the case statement to execute again. However, I end up in an infinite loop if I enter any value other than 1 through 4.

1st - How do I nest a case statement inside a while loop?

2nd - How do I make this script require the user input a value between 1 - 4

#!/bin/bash                                    

echo "What is your favorite Ninja Trutle?"     

echo "1 - Raphael."                            
echo "2 - Leonardo."                           
echo "3 - Michelangelo"                        
echo "4 - Donatello"                           

read TURTLE;                                   
COUNTER=0;                                     

while [ $COUNTER -eq 0 ]                       
do                                             
   $COUNTER=$(( $COUNTER + 1 ))                

   case $TURTLE in                             
      1) echo "Raphael is cool, but rude.";;   
      2) echo "Leonardo leads.";;              
      3) echo "Michelangelo is a party dude.";;
      4) echo "Donatello does machines.";;     
      *) echo "Did you even watch the show?"   
         $COUNTER=0                            
         ;;                                    
   esac                                        
done

Thanks for any help provided.

Answer 1

The error is in the lines in which you increment COUNTER. The $ symbol is used when you want to dereference the name of a variable to get its value. It's not used when you assign a value to the variable. Those lines should read:

COUNTER=$(( $COUNTER + 1 ))

and

COUNTER=0

Also, since the case command is inside the while loop, I assume you want to prompt the user again if he enters an invalid value. If that's so, you should put the read statement inside the while loop as well.