5 ms·
Shell scripting with Elixir
- DeathArrow 3y agoAs I am in the process of learning F# I am considering using it for scripting.
- thibaut_barrere 3y agoI have read good things about that!
- miloandmilk 3y agoMe too!
- ryanjshaw 3y agoFor personal stuff I use F# or C# (less and less, these days) for everything unless it's chaining together other command line tools in a way they're explicitly designed for. I've tried PowerShell and can't stand it. I have 20+ years of .NET, VS IDE and debugger experience I can leverage - it doesn't make sense for me to use anything else.
- hresvelgr 3y agoShell scripting in Elixir is like leaf-blowing your driveway with a helicopter.
- diggan 3y agoAwesome, but too expensive to be within reach of the ordinary person and more harmful to the environment compared to alternative methods?
- bryanrasmussen 3y agoelevator leaf blowing might be harmful to the environment but whats the argument about elixir in this analogy?
- diggan 3y agoI have no idea what parent is trying to say with their analogy, I'm trying to tease out some meaning from what they said. If anything, Elixir would be more energy efficient than bash as far as I can tell.
- fredrikholm 3y ago> Elixir would be more energy efficient than bash as far as I can tell For long running scripts perhaps. BEAM idles at ~50Mb, and startup is often more than 500ms. Eg: $ time ./hello hello world real 0m0,009s user 0m0,003s sys 0m0,007s $ time elixir hello.exs hello world real 0m0,755s user 0m0,992s sys 0m0,304s Where the first example is a BASH script.
- throwawaymaths 3y agoYes because when you load elixir you're loading the entire gOddamn Erlang VM. Which you might want for things like reliable parallel downloading, but you don't for hello world.
- toast0 3y agoI don't know that you'll get it down to 10 ms, but you can get beam startup a lot faster if you adjust parameters. The default startup does a lot of things you simply don't need in most shell scripts. Starting a bunch of threads, setting up dist, I can't remember what else off the top of my head.
- fredrikholm 3y agoEven without the shell and with epmd turned off we're still in the ball bark of 200-300ms: $ time erl -eval 'io:format("~s~n", [os:cmd("echo hello world")]), halt(0, [{flush, false}]).' -noshell -start_epmd false hello world real 0m0,332s user 0m0,461s sys 0m0,092s I spent some time last year trying to get those numbers down but this is as far as I made it. Do you know of any more flags that might help?
- thibaut_barrere 3y agoIf your script needs to do things like reliable HTTP querying and JSON parsing, I would say using Elixir (once you get used to it) won’t be harmful in any way, quite the contrary. Interestingly, what drove me to Ruby initially is exactly writing scripting tasks in a C#/C++ culture where Ruby would have been considered harmful. Now Elixir can be used for the same type of tasks, but only better (eg: trivial parallelized downloads!)
- neonsunset 3y agoF# and C# are very different to C++ in this regard. Parallel downloads in C# boil down to using var http = new HttpClient(); var urls = new[] { "http://example.com/file1.jpg", "http://example.com/file2.jpg", /* ... */ }; var files = await Task.WhenAll( urls.Select(http.GetByteArrayAsync)); (you can replace '.GetByteArrayAsync' with .GetFromJsonAsync, .GetStreamAsync and more depending on your needs and e.g. forward the incoming data directly to files on the disk or another source)
- lionkor 3y agoYou should, if you can?
- adityaathalye 3y agoAbsolutely. What is life without any fun?
- thibaut_barrere 3y agoAhaha, in a good way. Recently I have used Elixir scripts to mass-parallel-download numerous HTTP resources and do some stats on them, and it is exactly the feeling I had.
- dtx1 3y agoSuprisingly relevant https://www.youtube.com/watch?v=Ss6VBYLjMJQ https://www.youtube.com/watch?v=Ss6VBYLjMJQ
- wturner 3y agoI envision the creation of a GenServer for each and every file on your system, using this to duplicate them by the thousands, then deleting them in a timed contraction over and over and over again. I call this, "the blowcopter".
- Too 3y agoStill better than the inverse, that lots of scripters are doing; Building a helicopter out of a leaf-blower.
- datadeft 3y agoOne detail I really like about this is that you can install packages during the script run. Mix.install([ {:req, "~> 0.2"}, {:floki, "~> 0.30.0"} ])
- lambdaba 3y agoRuby can do this too: require 'bundler/inline' gemfile do source 'https://rubygems.org' gem 'json', require: false gem 'nap', require: 'rest' gem 'cocoapods', '~> 0.34.1' end
- behnamoh 3y agoCan't Python do the same? Like !pip install blahblah
- gkbrk 3y agoThat's not Python syntax. It's a Jupyter extension.
- behnamoh 3y agoRight, but Python can run command line code in subprocesses too, so it should be possible to run a pip install jupyter command inside Python.
- networked 3y agoThe problem is that installing dependencies for the user or globally will lead to version conflict. You need a separate virtual environment or a custom installation directory for each script to avoid conflicts. There are script runners and copy-pastable code snippets for Python that handle this. They automatically create the virtual environment and install the dependencies when the script runs. I have bookmarked several in https://github.com/stars/dbohdan/lists/python-scripts-with-deps https://github.com/stars/dbohdan/lists/python-scripts-with-d... (disclosure: not only is this my list, it also includes my project).
- adityaathalye 3y agoShell scripting with ideas from Elixir, chiefly, functional programming style would be profitable too. As an avowed (mostly) functional programmer, I do it FP style [1]. Of course, one can take a Shell script only so far. Eventually a Real Programming Language is the inescapable (pun intended) conclusion. [Insert "Always was" meme]. [1] I wrote about it here. https://www.evalapply.org/posts/shell-aint-a-bad-place-to-fp-part-2-functions-as-unix-tools/ https://www.evalapply.org/posts/shell-aint-a-bad-place-to-fp...
- bruh2 3y agoThat was so cool. Kind of an eye-opener. Bookmarked, thank you!
- adityaathalye 3y agoThank you for the kind remark. It so happened that I picked up shell scripting on the job at a workplace full of FP nerds. Pipelined code felt eerily familiar. Then at some point I read that Archmage McIlroy, a mathematician by training, invented the pipe. That was a lightbulb moment; a big reason why Functional style works as well as it does. Pipes are a mathematical idea. That whole series of posts is basically a glorified bookmark for yours truly. Tactics and tricks accumulated over the years. I refer back to bits and bobs from time to time. Writing them was a lot of, ah, fn.
- giovannibonetti 3y agoThis Bash library [1] is very handy to make your scripts more functional. [1] https://github.com/ssledz/bash-fun https://github.com/ssledz/bash-fun
- adityaathalye 3y agoI feel like I've seen this one before. Thanks for bubbling it back up in my brain. I think `map`, `filter`, and `reduce` (or `accumulate`) are automatic in pipelines; and have usually been enough for me. Still, it has a bunch of stuff one can pinch in a hurry. Starred!
- irjoe 3y agoYou can also use anonymous functions if you find the module syntax a little terse or clunky for shell scripting. double = fn a -> add.(a, a) end double.(4) It starts to look a bit like a weird untyped OCaml / F# if you use pattern matching: f = fn x, y when x > 0 -> x + y x, y -> x * y end
- losvedir 3y agoEver since Elixir 1.12, which introduced the `Mix.install[..]` at the beginning of the script, Elixir has been awesome for this sort of thing. Prior to that, it just wasn't worth it. I'm surprised the testing worked like that, without trying myself. When I last fiddled with it, I stole a page from how they recommend you do it in Livebook, and had `ExUnit.start(autorun: false)` at the top and `ExUnit.run()` at the bottom. I didn't realize you could just `ExUnit.start()` by itself up front. For anyone else who's tried an approach like this, have you managed to get doctests to work? I really like them, and think they're especially appropriate where you probably want lots of examples like here, but haven't been able to figure out how to stick them in ad-hoc scripts like this. I get some issue about the code not being compiled and available.
- vander_elst 3y agoThe more I use bash the more I appreciate it. It has a lot of sharp edges and quirks, but it's coincise, it works basically on all Unix systems and everyone knows (at least a bit of) it. A lot of attempts to fill this space have large gaps in this aspects. Not sure how this scores on those dimensions. For up to ~50 lines of script, bash is the most effective thing I found so far. Tried zsh, fish, python, ruby, but for such glue code bash rules.
- mhitza 3y ago> The more I use bash the more I appreciate it. That is true for sure if you write bash scripts quasi daily. However if you don't it becomes very easy to forget, at least for me. That's why I'm the type of person that tries to look out for alternatives in different languages. I've had and read from cover to cover, Bash, sed, and AWK books, yet when I have to get back to them I still only remeber the most fundamental features that I use every couple of days or weeks.
- noisy_boy 3y agoMy rule of thumb for moving from bash to Perl/Python etc is when I need to start implementing multiple arrays and associative arrays to get the job done.
- vander_elst 3y agoAgree
- SomeoneFromCA 3y agoI found that browsing through the bash source makes remembering things about how to use bash easier. It is simple enough to see the gears at work, comapared to say python interpreter sources.
- behnamoh 3y agodon't those quirks and sharp edges leave security holes in the script tho?