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Bash Until the loop ends

I have been playing around with bash programming. I wrote a simple bash program that takes input from the reader. If the reader has typed the string "bye", the while loop ends. So the program is pretty simple, I wrote something like this

#!/bin/sh
inputString="hello"
while [ inputString != "bye" ]
do
    echo "Please write something (bye to quit)"
    read inputString
    echo "You typed : ${inputString}"
done

It works great as long as the user doesn't enter two words at a time.

If the user enters something like this

bye bye

A program crash causing the following error:

./WhileLoop.sh: 5: [: bye: unexpected operator

How can I change the code so that the program can accept multiple inputs?

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3 answers


Place double quotes around inputString

in while

. Without double quotes, if your variable is empty it will throw an error.

Update:



There's a typo on the script, add $

before inputString

, do the variable replacement:while [ "$inputString" != "bye" ]

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In bash

4+ you can also:



while read -r -p 'Please write something (bye to quit)>' ans
do
   echo "your answer =$ans="
   #convert the $ans to lowercase to match "BYE"
   #use matching to match "bye bye" or "byeanythinghere"
   #in case of double [[ don't needed the "", but never harm, so using it
   [[ "${ans,,}" =~ bye.* ]] && exit 0
   #[[ ${ans,,} =~ bye.* ]] && exit 0   #works too
   echo "not bye - yet"
done
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Use the $ variable in front of the variable so that it gets expanded. $ InputString

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