lsofer VS mycmd

/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

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.

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