Very useful for renaming a variable: * to search “word” under cursor. Try this with hlsearch on::set hlsearch. Then cw to change a match. Alternate n and . to quickly rename more occurrences of the word. Do a :noh to get rid of the highlighting. Maybe try :set noinc, some people prefer the traditional “non-incremental” search.

Do all this in normal mode. Vim experts leave insert mode as soon as possible. Almost forgot: Pressing C-c takes you back to normal mode without leaving home row.

Most important advice: Never touch arrow keys. Keep your fingers on the home row. Learn hjkl movement (focus on j and k, they are more important). Then get faster by using b, w, f, o, O, A, I, C-d and all the rest. Learn about J, it’s cool. You won’t get far without u and C-r though.

Critically important advice for fellow Europeans: If you care about vim, consider learning the US keyboard layout. Default bindings are not convenient in other layouts like qwertz (where is forward slash on qwertz? Hello?), and learning US layout might be easier than learning to customize vim. On a typical modern Linux system, there are US layout variants that still allow typing Umlauts, like EurKey or “DE-US”, where you type ä by pressing RightAlt+a, for example.

I use cat (as root) to write ISO to flash drive. Anything wrong with that?

in [[ there is generally no need for quoting, except the right hand side of an = comparison

in [[, empty strings are falsy, so this also works:

[[ ! $VARIABLE1 && ! $VARIABLE2 ]] && echo "OK"

The variables need a dollar sign: $VARIABLE1

help test shows what -n and -z do.

Never use a && b || c. It is not the same as if a; then b; else c; fi: when a succeeds but b fails, it will run both b and c.

I would not bother with [ unless you absolutely need compatibility with non-bash shells.

no I don’t have that choice, see my other comment

This, except I won’t buy an apple device (unless forced to: in Germany an i-bad is required in many high schools, yes you need to pay for it in full with your own money, yes it needs to be an i-bad they even require a specific model)

Some employers offer intellij ultimate subscriptions. It’s even mandatory in some teams. The devs don’t have to pay out of their own pocket. But I think many of them are hooked and will lobby to keep the subscription going.

Try opening a terminal an typing echo 'Hello World!' My two cents: You can forget about Linux for a while. Using a terminal is more important. Here’s a classic guide: https://mywiki.wooledge.org/BashGuide