bash + while loop with regular expression [closed]

Question

The following loop is looping when number is less than 1 or greater than 45 but it fails when the answer includes special characters such as [ % & * # ] etc

What can I change in the code in order to support this issue?

a=1
b=45


while [[ $answer -lt $a ]] || [[ $answer -gt $b ]]
do

echo -n "please answer"
read answer
done

Answer 1

You might rethink the whole concept. This is a simple snippet that will get you going.

#!/usr/bin/env bash

a=1
b=45


while read -p 'Please answer: ' answer
do
   re=$(printf '%s\n' "$answer" | tr -dc '[[:digit:]]')
   if ((re < a || re > b)); then
       read -p 'Please answer: ' $re
   else
       echo "Loop ended"
       exit 
   fi
 done

Answer 2

try this:

#!/bin/bash
#
a=1
b=45
#
while [[ $answer -lt $a || $answer -gt $b ]]; do

read -p "please answer: " answer
answer=$(echo "$answer" | tr -dc '[:alnum:]\n\r')

done

The answer=$(echo "$answer" | tr -dc '[:alnum:]\n\r') line will strip any special characters from the answer and reset the variable to the new value.