youtube视频下载
wget http://youtube-dl.org/latest/youtube-dl -O /var/www/html/youtube-dl
chmod a+x /usr/local/bin/youtube-dl
常见用法：youtube-dl -h
列出所有格式视频：youtube-dl -F [URL]
下载指定格式视频：youtube-dl --ignore-errors --write-auto-sub -f 22 https://www.youtube.com/watch?v=-Ey4oYSgVxk
youtube视频下载
古有内事不决问张昭，外事不决问周瑜；
今有生活不懂问百度，学术不懂问谷歌。
(SunQuan)The inner undecided ask ZhangZhao, the outer undecided ask ZhouYu.
(I)Life unknown ask Baidu, academic unknown ask Google.