bash-core VS mycmd

Error handling is also atrocious. Doing set -e fixes some issues, but there are plenty of valid cases in which one of your commands will have an error, and your script will continue execution like nothing ever happened. And, in the case of an error, as I'm sure you have realized, diagnostics are absolutely terrible. You're extremely lucky to get a line number (which I think was only added since Bash 5.1), but that's it. If you want anything more, like a stacktrace, you're stuck in the water. I have developed a library, bash-core, to help with this, but the stacktrace handling acts unexpectedly if there are errors within subshells.

I'm quite happy to see that something Bash-related is on Hacker News! Unfortunately it seems that I don't really agree with much the author...

While I do agree that it would be nice to be able to have 'local' functions and have inter-function cleanup work better, the logical conclusion for me was not to use function subshells. Since the use case is for larger programs (where different functions may want to have their own cleanup mechanisms), I'm opting to go for more of a library route. For example, I'm working on a Bash library that includes a function to allow different sources to add (and remove) functions to the same `TRAP`. A similar function may be useful, possibly involving the `RETURN` trap and the `-T` flag. Obviously, using a package manager for _Bash_ of all languages brings in a lot of overhead, but I think it can be quite powerful, especially with a potential "Bundle" feature that makes scripts work without the package manager.

Concerning specifically the use of subshells, (as other commenters have pointed out) it significantly reduces performance. I also disagree that dynamic scoping is necessarily bad for Bash. I find it quite useful when I need to use various common functions to manipulate a variable - since modifying and 'returning' variables from a function is usually either slow or verbose with Bash. Admittedly though, this feature is quite annoying at times - for example, most public functions in my Bash package manager[2] all have their variables prefixed with two underscores - because they `source` all the shell scripts of all package dependencies - so I want to be extra certain nothing weird happens

[1] https://github.com/hyperupcall/bash-core/blob/a17ab0a8b6070f...

Woah, this is very cool. I may try to adopt this.

I recently discovered, similar to the author of the post for this thread, that local variables are dynamically scoped.

I have been writing a lot more shell scripts lately, using a "library" [1] of sorts I've been writing. When I was debugging one of my scripts that uses mycmd, I discovered that I had failed to declare some of my variables local and they were leaking out to the global scope.

I had recently added functionality to call a set of functions on script exit, so I added something that would output the defined variables, in hopes that I could write something that will output them at the beginning and then the end and show the difference. I was surprised when variables defined in my dispatch function [2] for those at exit functions were showing up, even though they were definitely defined as local. It was then that I dug around and discovered the dynamic scope of variables.

I've been trying to figure out how to accomplish what I desire but exclude those variables from calling functions. I haven't been able to find an obvious way to see if the variable is coming from a calling function. I might be able to use techniques like you've pointed out in your linked post to add the tracing that I want. Still need to think more on this.

---

[1] https://github.com/travisbhartwell/mycmd