Shell Programming and Scripting

read var
if [ $var = "q" ]
then
echo "yes... quitting"
exit 1
fi

loop=1
while [ loop -eq "1" ]
   echo "Type F for first choice"
   read firstChoice
   echo "Type S for second choice"
   read secondChoice
   if [ "$firstChoice" = "F" ]; then
         echo "This is the first choice"
   elif [ "$secondChoice" = "S" ]; then
         echo "This is the second choice"
   else
         echo "no choice"
         loop=0
         exit 1   
   fi

  how do i catch the keyboard input for $var to quit any time? 
  if [ $var = "q" ]; then
      echo "yes... quitting"
    exit 1
   fi
done

check() {
  if [ $1 = "q" ]; then
      echo "yes... quitting"
    exit 1
   fi
 }

loop=1
while [ loop -eq "1" ]
   echo "Type F for first choice"
   read firstChoice
   #
   check firstChoice
   #
   echo "Type S for second choice"
   read secondChoice
   #
   check secondChoice
   #
   if [ "$firstChoice" = "F" ]; then
         echo "This is the first choice"
   elif [ "$secondChoice" = "S" ]; then
         echo "This is the second choice"
   else
         echo "no choice"
         loop=0
         exit 1   
   fi
done

QUIT () {
            if [ $firstChoice = "q" ] || [ $secondChoice = "q" ]; then
              exit 1
            fi
             }

loop=1
while [ loop -eq "1" ]
   echo "Type F for first choice"
   read firstChoice
QUIT
   echo "Type S for second choice"
   read secondChoice
QUIT
   if [ "$firstChoice" = "F" ]; then
         echo "This is the first choice"
   elif [ "$secondChoice" = "S" ]; then
         echo "This is the second choice"
   else
         echo "no choice"
         loop=0
         exit 1   
   fi