https://www.cnblogs.com/ggjucheng/archive/2013/01/13/2858470.html
http://wiki.jikexueyuan.com/project/shell-learning/awk-command.html
https://www.cnblogs.com/ggjucheng/archive/2013/01/13/2858470.html
http://wiki.jikexueyuan.com/project/shell-learning/awk-command.html