授权

cd /Users/lion/Downloads/shell-test-demos
chmod u+x *.sh

read_user_enter.sh

#!/bin/bash

printHelp() {
    echo "1. hello"
    echo "2. world"
    echo "0. exit"
}

printHelp

number=""
while [ -z $number ]; do
    read -p "enter a number: " number
    if [ "$number" == "0" ]; then
        exit 1
    elif [ "$number" == "1" ]; then
         echo "hello"
        number=""
    elif [ "$number" == "2" ]; then
        echo "world"
        number=""
    else
        printHelp
        number=""
    fi
done