Nice one! I love those weird bash tricks.
Some of the examples here are interesting, but they show parameter substitution more than colon itself: https://tldp.org/LDP/abs/html/parameter-substitution.html
In small scopes, I tend to inline the `:?` validation inside the arg of the command. `echo "${1:? first param required}"`
Another usecase is to use colon in the body of a while loop, while doing work in the condition of the loop.
while rlwrap -o -S'>> ' tr a-z A-Z ; do :; done
I've also written about this and other bash tricks over the years in https://github.com/kidd/scripting-field-guide/blob/master/bo.... You might like them :)
I hate weird bash tricks with a passion.
The extent to which the script author gets to feel smart and efficient is exactly the extent to which the future reader of the script gets to feel like an idiot.
So true. I think most of us who learned "advanced" bash is after being tired of feeling like an idiot looking at long bash scripts.
Usually, those scripts are written by people who didn't learn the "weird tricks", and use global variables (they didn't learn that `local` creates local variables), for example.
In bash, many times the "dumb way" takes 10 times more lines, and it's probably buggier than the "smart tricky way". So, in the end it's your choice what side you pick, and when to stop. Or, use a "real programming language" (I hate when people say this LOL)
After a while, you get a bit of stockholm syndrome, and you're just fine with bash as an orchestration language, and lean into unix principles. I accept its limitations, and I think it keeps me on my toes as it repels bloat.
idk if you were expecting an answer, but bash lives in this liminal space in the tower of languages that is worth a thought.
The only upside of weird bash tricks is there's so much bash out there that the LLMs are really well trained on it - so you won't have to read the script, just the tests.