另一种验证IP的方法。要点： ①直接把变量值包含的空格替换为下划线 ②匹配IP的正则表达式要更具体 ③在Bash中测试regex **不要** 使用任何引号！ https://stackoverflow.com/a/13015572/3025050

validation (name and IP address) in bash.sh

#!/bin/bash

read name    
while [[ ! "$name" =~ '[A-Za-z ]' ]]; do
    read -p "Wrong name format. Re-enter: " name
done

name="${name// /_}"

read ip
while [[ ! "$ip" =~ '^((25[0-5]|2[0-4][0-9]|[01][0-9][0-9]|[0-9]{1,2})[.]){3}(25[0-5]|2[0-4][0-9]|[01][0-9][0-9]|[0-9]{1,2})$' ]]; do
    read -p "Not an IP. Re-enter: " ip
done