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https://ryanstutorials.net/linuxtutorial/commandline.php
http://linuxcommand.org/lc3_lts0010.php
https://swcarpentry.github.io/shell-novice/reference/
https://swcarpentry.github.io/shell-novice/
https://dev.to/awwsmm/101-bash-commands-and-tips-for-beginners-to-experts-30je
https://www.katacoda.com/courses/centos/playground