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Comment by hresvelgr | Hacker News Reader

Shell scripting in Elixir is like leaf-blowing your driveway with a helicopter.

Ahaha, 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.

Suprisingly relevant https://www.youtube.com/watch?v=Ss6VBYLjMJQ

Still better than the inverse, that lots of scripters are doing; Building a helicopter out of a leaf-blower.

I 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".

Awesome, but too expensive to be within reach of the ordinary person and more harmful to the environment compared to alternative methods?

elevator leaf blowing might be harmful to the environment but whats the argument about elixir in this analogy?

I 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.

> 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.

Yes 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.

I 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.

Even 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?

Try -boot no_dot_erlang

A couple years ago that got me to 100 ms

https://news.ycombinator.com/item?id=25243246

Today's measurements with FreeBSD 13.2 on the same Pentium G3470

time /bin/sh -c "echo hi"

   hi

   real    0m0.004s
   user    0m0.001s
   sys     0m0.002s

time /usr/local/bin/bash -c "echo hi" hi

   hi

   real    0m0.006s
   user    0m0.007s
   sys     0m0.000s

time /usr/local/lib/erlang26/bin/erl -eval 'io:format("hi~n"), halt(0, [{flush, false}])'

   Erlang/OTP 26 [erts-14.2.1] [source] [64-bit] [smp:2:2] [ds:2:2:10] [async-threads:1] [jit:ns] [dtrace] [sharing-preserving]

   hi

   real    0m0.197s
   user    0m0.178s
   sys     0m0.018s

time /usr/local/lib/erlang26/bin/erl -eval 'io:format("hi~n"), halt(0, [{flush, false}])' -noshell -start_epmd false -boot no_dot_erlang

   hi

   real    0m0.183s
   user    0m0.181s
   sys     0m0.011s

This doesn't look very good, actually! FreeBSD has OTP 21-26 available through pkg, I ran the same thing on each of them several times to warm up, and get (real time):

   21:  81ms
   22:  81ms
   23:  74ms
   24: 129ms
   25: 135ms
   26: 177ms

So maybe there's some new stuff that needs to be avoided now.

It was your original post that set me on course for experimenting with startup times, cheers!

Unfortunately, that final flag doesn't change much on 26 for me. IIRC I dropped a bunch of flags after concluding that no shell and no epmd were the only flags that I noticed improvements with.

Yeah, it looks like it got a lot worse. I don't think it's JIT, because I ran a test with a 32-bit version of OTP 26 (JIT is only available for 64-bit x86 and arm). But I'm not sure what it is.

Send me an email (in profile), and I'll try to find some time to look closer.

If 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!)

F# 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)

You should, if you can?

Absolutely. What is life without any fun?

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