Elixir checks most of those boxes. If you want a good functional scriptibg language, Elixir soynds like the go to. Some lisp language like guile should also be sufficient, and probably have a lighter footprint.

This requirement stands out though:

has a simple/straightforward setup (ideally, it should be a single executable that I can just copy to a remote system, use to run a script and then delete)

Thats basically what ansible does. If you plan on doing this to multiple machines you should just use ansible. Also how do you plan on ensuring the scripting interpreter is installed on the machines?

I would go with Guile, because it is built-in to the Guix Package Manager which is a really good general-purpose package manager.

It ticks several of your boxes:

• has a CLI interpreter
• is a general purpose language, Scheme, amd compliant with revisions 5, 6, and 7 of the language standard
• allows writing in a functional style (it is one of the original functional programming languages)
• small disk footprint, but still large enough to be "batteries included"
• decent documentation, especially if you use Emacs
• simple setup: not so much, unless you are using Guix to begin with. The standard distribution ships with lots of pre-built bytecode files, you need an installer script to install everything.

It also has pretty good libraries for system maintenance and reporting:

• File-Tree-Walk
• A simple web server
• XML parsing

There's always nushell. It's fairly new, not quite to 1.0 yet (0.96.1 at time of writing), but the constant breaking changes seemed to have stopped. It hits all your points and it's quite fun to use when writing scripts. Bonus that it's also pretty much tailor-made to manipulate data.

Perl or python for things likely to already be there. Maybe ruby or PHP if you must. I used to work in groovy a lot but I think it requires the JVM

Quickly came to write "AWK!!!!!!!!!" but yeah... you don't want its superiority... 😜

Perl would be my candidate for more advanced text handling than what sh can do.

Never used Lua but I think it's fun.

If nothing else works, just learn C/Rust. There's plenty of that on Linux systems, I think you'll be able to manage. Yes, it doesn't meet a lot of your requirements.

https://nim-lang.org/

Why not give (Common)LISP a try?

posix sh + awk for manipulating data?

You should probably check out Guile.

Why does it need to be a scripting (by this I assume interpreted) language? For your requirements - particularly lightweight distribution - a precompiled binary seems more appropriate. Maybe look into Go, which is a pretty simple language that can be easily compiled to native binaries.

Could use a hipster shell like fish, nushell or elvish. I know the latter two have the functional support you're looking for.

It is possible to wrap something like python into a single file, which is extracted (using standard shell tools) into a tmpdir at runtime.

You might also consider languages that can compile to static binaries - something like nim (python like syntax), although you could also make use of nimscript. Imagine nimscript as your own extensible interpreter.

Similarly, golang has some extensible scripting languages like https://github.com/traefik/yaegi - go has the advantage of easy cross compiling if you need to support different machine architectures.

perl might be on all your systems. It’s kind-of a legacy, but still actively developed. It’s not a great language: it looks like bash scripting on steroids. But if you just need to write some small scripts with a language more powerful than awk or bash, it does the job. If perl isn’t on all of your systems already, then I would choose a better scripting language.

You could use Ansible for automation just keep in mind it needs python.

Bro seriously just slap pyenv + pyenv-virtualenv on your systems and you’re good to go. They’re absolutely trivial to install. Iirc the latter is not a thing in windows, but if you’re stuck on windows for some reason and doing any serious scripting, you should be using WSL anyways.

@gomp Small footprint? Why not try forth. https://forth-standard.org/