If not equal to then loop

Shell Programming and Scripting
1

How do I go about amending this simple script that prompts for a yes/no response so that if neither Y or N are entered it will loop back back to the original prompt

#!/bin/ksh
echo "Enter yes of no"
read answer
if [ $answer == y -o $answer == Y ]
then
  echo "You selected yes"
elif [ $answer == n -o $answer == N ]
then
  echo "You selected no"
elif [ $answer != y -o $answer != Y -o $answer != n -o $answer != N ]
then
  echo "Invalid Option"
fi

Thanks

2

Hi

while [ 1 ]
do
echo "Enter yes of no"
read answer
if [ $answer == y -o $answer == Y ]
then
echo "You selected yes"
break
elif [ $answer == n -o $answer == N ]
then
echo "You selected no"
break
elif [ $answer != y -o $answer != Y -o $answer != n -o $answer != N ]
then
echo "Invalid Option. Try again"
fi
done

Guru.

3

Using case statement:

echo "Enter y/n"
while read answer
do
  case $answer in 
    y|Y) echo "You selected yes" ;;
    n|N) echo "You selected no" ;;
    *)   echo "Invalid Option. Try again"
         continue ;;
  esac
  break
done
4

Thanks to both of you.

Much appreciated.

5

You can get this achieved using until loop.

E.g

#!/bin/ksh
echo "Enter yes of no"
read answer

until [ $answer == y -o $answer == Y -o $answer == n -o $answer == N ]
do
echo "Sorry, Please Enter yes of no"
read answer
done

if [ $answer == y -o $answer == Y ]
then
  echo "You selected yes"
    elif [ $answer == n -o $answer == N ]
      then
          echo "You selected no"
	      elif [ $answer != y -o $answer != Y -o $answer != n -o $answer != N ]
	          then
		        echo "Invalid Option"
			      fi
6

Thanks for the help on this, how would I expand it to prompt for two responses and loop back to the original prompt

i.e.

echo "Enter a choice"
read choice 
 
echo "confirm $choice is correct y/n"
read confirm
 
if [ $confirm == y -o $confirm == Y ]
then do something
 
elif [ $confirm == n -o $confirm == N ]
then loop back to the enter a choice prompt
 
elif [ $confirm != y -o $confirm != Y -o $confirm != n -o $confirm != N ]
then
echo "Invalid Option" and loop back to confirm choice