Shell Redirect

http://www.tldp.org/LDP/abs/html/io-redirection.html

http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-3.html

http://blog.dorm7.com/post/26965043036/std-error-std-out

http://fourdollars.blogspot.tw/2013/03/bash-redirection.html