https://stackoverflow.com/questions/5891342/modify-conf-file-with-shell-script
http://www.grymoire.com/Unix/Sed.html
https://www.amazon.com/Practical-Guide-Commands-Editors-Programming/dp/0134774604/ref=sr_1_4?ie=UTF8&qid=1522319499&sr=8-4&keywords=Linux+shell
https://download.csdn.net/download/blkf/5776001
https://www.amazon.com/Linux-Command-Line-Complete-Introduction/dp/1593273894/ref=sr_1_6?ie=UTF8&qid=1522319499&sr=8-6&keywords=Linux+shell
https://download.csdn.net/download/u011433684/10024901
https://www.amazon.com/Linux-Command-Shell-Scripting-Bible/dp/111898384X/ref=sr_1_3?ie=UTF8&qid=1522319499&sr=8-3&keywords=Linux+shell