Library Runtime

A lightweight erlang runtime. No processes are started by the init process. No modules other than a small see runtime are loaded. You define a module with a main function which is called. Upon completion of the main funtion the process stops.

Such a main function can start supervision trees and other long lived processes.

The aim of this project is to write a runtime as library. I.e. you explicitly require all modules and start all processes that your program needs. All configuration is code in the main loop.

i.e. in the future

import gleam/logger
import gleam/ssl

pub fn main() {
  assert Ok(pid) = logger.start(config)
  assert Ok(ssl) = ssl.start(config)
  // etc
}

Usage

Ergonomics of this can definetly be improved. But for now the steps are as follows

1. Write a Gleam program in /src
2. run ./build
3. run ./run name (where name is the name of your module that has the main function)

Notes

Counting loaded modules and processes

code:all_loaded().
length(processes()).
length(registered()).

Erlang System Principles

https://erlang.org/doc/system_principles/system_principles.html#default_boot_scripts

Explains boot scripts, and enumerates default boot scripts. There IS a boot script without SASL.

Erlang Runtime options

http://erlang.org/doc/man/erl.html

-s module Tries to start with a call to module:start() -s module function Tries to start with a call to module:function()

More than one -s can be specified. To start a program that stops. use. erl -s my_module main -s init stop -noshell

-extra everything after extra is considered plain arguments and can be loaded using init:get_plain_arguments()

-r works the same as -s except with this comment in the docs

Because of the limited length of atoms, it is recommended to use -run instead.

Mode

interactive/embedded

Default mode is interactive, it loads code files on demand. code:get_mode(). allows you to see which it is at runtime.

Erlang preloaded source

https://github.com/erlang/otp/tree/master/erts/preloaded/src