CODEWITHSUNDEEP
linuxbashwhile-loop
mirmdasif
mirmdasif

Reputation: 6354

Bash While loop Not Ending

I was playing with bash programming. I have written a simple bash program which takes input from reader. If reader typed the string "bye" the while loop ends. So the program is pretty simple I have written 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 perfectly until user type two words at a time.

If user type something like this 

bye bye

Program crashes giving the following error

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

How can i modify the code so that program can take multiple input?

Upvotes: 3

Views: 2079

Answers (3)

Zulu
Zulu

Reputation: 9285

Put double quotes around inputString in while's condition. Without double quotes, if your variable is empty, it will raise a error.

Update:

There's a typo on script, add $ before inputString, make variable substitution: while [ "$inputString" != "bye" ]

Upvotes: 3

clt60
clt60

Reputation: 63974

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

Upvotes: 2

Austin Phillips
Austin Phillips

Reputation: 15776

Use a $ in front of a variable to have it expanded. $inputString

Upvotes: 1

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