用Linux命令行獲取本機外網IP地址
$ curl ifconfig.me
$ curl icanhazip.com
$ curl ident.me
$ curl ipecho.net/plain
$ curl whatismyip.akamai.com
$ curl tnx.nl/ip
$ curl myip.dnsomatic.com
$ curl ip.appspot.com
$ curl -s checkip.dyndns.org | sed 's/.*IP Address: \([0-9\.]*\).*/\1/g'