stlink

It's not about the best way to behave differently at runtime and sometimes call exit depending on how the script was invoked, it's about the idea that a scripting language would SUPPORT and ENCOURAGE writing that kind of script, with a special magic built-in variable and a section in the already-complex documentation encouraging its use. Scripts should not behave differently depending on if they were invoked from other scripts, and modular reusable libraries should never take it upon themselves to call "exit" when there's an error. The way to control the flow of recursive functions is by passing explicit parameters (like the recursion depth, or a data structure to walk, or an error callback), not reflecting on the depth of the runtime stack or looking at how the function was called. If bash is too weak to handle errors, or exceptions, or