As silly as it sounds, when I was a new Unix SysAdmin, I read the entirety of "man 1 bash", which includes all bash builtins. I found that it improved by bash-foo 100x simply by knowing about so many of the utilities. I also took some cliff notes for things that seemed generally useful.
I did it for an hour or so a night for a week or so.
That being said, a few of my personal favorites to memorize:
* Parameter expansion: https://www.gnu.org/software/bash/manual/html_node/Shell-Par...
* All of test(1) as you can use them in any if statement (/usr/bin/[ is a real command!): https://linux.die.net/man/1/test
* Knowing most of the bash internal variables: http://tldp.org/LDP/abs/html/internalvariables.html
* Keyboard shortcuts and how they are useful. A few example: CTRL-l (no need to ever use /usr/bin/clear), CTRL-k, CTRL-u, CTRL-e, CTRL-a, CTRL-w, CTRL-arrow left, CTRL-arrow right, CTRL-r (history reverse search with find as you type autocomplete)
The best way you can learn the shell is by using Linux as your primary desktop for at least a few months. You'll get very proficient very quickly by doing that.
I did it for an hour or so a night for a week or so.
That being said, a few of my personal favorites to memorize:
* Parameter expansion: https://www.gnu.org/software/bash/manual/html_node/Shell-Par...
* All of test(1) as you can use them in any if statement (/usr/bin/[ is a real command!): https://linux.die.net/man/1/test
* Knowing most of the bash internal variables: http://tldp.org/LDP/abs/html/internalvariables.html
* Keyboard shortcuts and how they are useful. A few example: CTRL-l (no need to ever use /usr/bin/clear), CTRL-k, CTRL-u, CTRL-e, CTRL-a, CTRL-w, CTRL-arrow left, CTRL-arrow right, CTRL-r (history reverse search with find as you type autocomplete)
The best way you can learn the shell is by using Linux as your primary desktop for at least a few months. You'll get very proficient very quickly by doing that.