Manual Refer To

• https://www.tutorialspoint.com/awk/index.htm # 源起之篇
• https://segmentfault.com/a/1190000007338373
• https://awk.readthedocs.io/en/latest/chapter-one.html

[root@centos77 ~]# awk --version
GNU Awk 4.0.2
Copyright (C) 1989, 1991-2012 Free Software Foundation.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see http://www.gnu.org/licenses/.