網上很多方法不行。其實很簡單，一句就ok：
brew install wget
命令一次过，在命令行测试下，
wget www.baidu.com
–2016-05-31 22:05:28–http://www.baidu.com/
Resolving www.baidu.com… 111.13.100.91, 111.13.100.92
Connecting to www.baidu.com|111.13.100.91|:80… connected.
HTTP request sent, awaiting response… 200 OK
Length: unspecified [text/html]
Saving to: ‘index.html’
index.html [ <=> ] 96.65K 68.0KB/s in 1.4s
2016-05-31 22:05:30 (68.0 KB/s) - ‘index.html’ saved [98974]
OK!
