lsofer VS bash-core

/proc is amazing once you get the hang of it and get a good understanding of what's all in there. Especially if you're doing low level performance tuning.

It's particularly helpful in larger infrastructures where tool the variability means differences in available tooling, and their output plus cli options. I'm sure /proc iteration has its own issues of variability across large infrastructres, but I haven't seen it. It's a fairly consistent API. Or at least it was, since I haven't touched a large infrastructure in some time.

When I got tired of `lsof` not being installed on hosts (or when its `-i` param isn't available) I ended up writing a script [1] that just iterates through /proc over ssh and grabs all inet sockets, environment variables, command line, etc from a set of hosts. Results in a null-delimited output that can then be fed into something like grafana to create network maps. Biggest problem with it is the use of pipes means all cores go to 100% for the few seconds it takes to run.

[1] https://github.com/red-bin/lsofer

Oh yeah, bash functions are great and absolutely abusable. Sometimes you need some grand hacks to get it to work well, but when it works well, it can do some magic. You can even export functions over ssh!

I wrote this a few years back which ran on bunches of hosts and fed into a infrastructure network mapper based on each hosts' open network sockets to other known hosts. It wasn't really feasible to install a set of tools on random hosts.. but I still had root ssh access across the board. So I needed something tool agnostic, short, auditable, and effectively guaranteed to work:

https://github.com/red-bin/lsofer/blob/master/lsofer.sh

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...