validate phone number shell script file code example

Example: how to validate a mobile number in shell script

#!/bin/bash
echo "Enter a phone number as XXXXXXXX: "
read phoneNumber
pat="^[0-9]{8}$"
while [[ ! $phoneNumber =~ $pat ]]
    do
    echo "Please enter a phone number as XXXXXXXX: "
    read phoneNumber
done
echo $phoneNumber