# Optimus

<img align="right" width="192" height="192" alt="Optimus avatar: Transformer's head shaped as a letter “O”" src="./assets/logo.png">

[![Build Status](](
[![Coverage Status](](
[![Module Version](](
[![Hex Docs](](
[![Total Download](](
[![Last Updated](](

A command line arguments parsing library for [Elixir](

It's aim is to take off the maximum possible amount of manual argument handling.
The intended use case is to configure Optimus parser, run it against the
command line and then do nothing but take completely validated
ready to use values.

The library was strongly inspired by the awesome [](
library. Optimus does not generally follow its design, but it tries to
follow the idea of zero manual manipulation with the values after the parser has
returned them.

## Installation

Add `optimus` to your list of dependencies in `mix.exs`:

def deps do
    {:optimus, "~> 0.2"}

## Example

Let's configure a CLI interface to an imaginary utility which reads data from
a file of the following format:

# timestamp, value
1481729245, 12.0
1481729245, 13.0
1481729246, 11.1

and outputs some statistic metrics of the values.
It also has a subcommand which validates the source file integrity.

defmodule Statcalc do
  def main(argv) do!(
      name: "statcalc",
      description: "Statistic metrics calculator",
      version: "1.2.3",
      author: "John Smith",
      about: "Utility for calculating statistic metrics of values read from a file for a certain period of time",
      allow_unknown_args: false,
      parse_double_dash: true,
      args: [
        infile: [
          value_name: "INPUT_FILE",
          help: "File with raw data",
          required: true,
          parser: :string
        outfile: [
          value_name: "OUTPUT_FILE",
          help: "File to write statistics to",
          required: false,
          parser: :string
      flags: [
        print_header: [
          short: "-h",
          long: "--print-header",
          help: "Specifies whether to print header before the outputs",
          multiple: false,
        verbosity: [
          short: "-v",
          help: "Verbosity level",
          multiple: true,
      options: [
        date_from: [
          value_name: "DATE_FROM",
          short: "-f",
          long: "--from",
          help: "Start date for the period",
          parser: fn(s) ->
            case Date.from_iso8601(s) do
              {:error, _} -> {:error, "invalid date"}
              {:ok, _} = ok -> ok
          required: true
        date_to: [
          value_name: "DATE_TO",
          short: "-t",
          long: "--to",
          help: "End date for the period",
          parser: fn(s) ->
            case Date.from_iso8601(s) do
              {:error, _} -> {:error, "invalid date"}
              {:ok, _} = ok -> ok
          required: false,
          default: &Date.utc_today/0
      subcommands: [
        validate: [
          name: "validate",
          about: "Validates the raw contents of a file",
          args: [
            file: [
              value_name: "FILE",
              help: "File with raw data to validate",
              required: true,
              parser: :string
    ) |> Optimus.parse!(argv) |> IO.inspect

(The whole sample code can be found in
[optimus_example]( repo.)

Nearly all of the configuration options above are not mandatory.

Also most configuration parameters are self-explanatory, except `parser`.
For options and positional arguments `parser` is a lambda which accepts a string argument and returns either
`{:ok, parsed_value}` or `{:error, string_reason}`. There are also some predefined parsers which are denoted by atoms:
`:string`, `:integer` and `:float`. No parser means that `:string` parser will be used.

Not required `options` can have a `default` value. Both a term (string, number, etc.) or a lambda with zero arity can be used.
If the `option` accepts `multiple` values, the `default` value should be a list, for example `[1.0]` or `fn -> ["x", "y"] end`.

Now if we try to launch our compiled escript without any args we'll see the following:

The following errors occurred:
- missing required arguments: INPUT_FILE
- missing required options: --from(-f), --to(-t)

    statcalc --help

to see available options

There are several things to note:
* the script exited (in `Optimus.parse!`) since we haven't received a valid set
of arguments;
* a list of errors is displayed (and it's as full as possible);
* a user is offered to launch `statcalc` with `--help` flag which is automatically
handled by Optimus.

If we launch `statcalc --help`, we'll see the following:

>./statcalc --help
Statistic metrics calculator 1.2.3
John Smith
Utility for calculating statistic metrics of values read from a file for a certain period of time

    statcalc [--print-header] --from DATE_FROM --to DATE_TO INPUT_FILE [OUTPUT_FILE]
    statcalc --version
    statcalc --help
    statcalc help subcommand


    INPUT_FILE         File with raw data
    OUTPUT_FILE        File to write statistics to


    -h, --print-header        Specifies whether to print header before the


    -f, --from        Start date for the period
    -t, --to          End date for the period  (default: 2017-12-20)


    validate        Validates the raw contents of a file


The things to note are:
* Optimus formed a formatted help information and also exited;
* it also offers some other autogenerated commands (`--version` and `help subcommand`).

Now if we finally produce a valid list of args, we'll have our arguments parsed:

>./statcalc --print-header -f 2016-01-01 -t 2016-02-01 infile.raw outfile.dat
  args: %{
    infile: "infile.raw",
    outfile: "outfile.dat"
  flags: %{
    print_header: true
  options: %{
    date_from: ~D[2016-01-01],
    date_to: ~D[2016-02-01]
  unknown: []

`Optimus.ParseResult` is a struct with four fields: `args`, `flags`, `options`,
which are maps, and `unknown`, which is a list. Things to note are:
* `unknown` list is always empty if we set `allow_unknown_args: false` for our
* values in `args`, `flags` and `options` maps are kept under keys specified in configuration;
* for options with `multiple: true` the value is a list;
* for flags without `multiple: true` the value is a boolean;
* for flags with `multiple: true` the value is an integer (representing the
  number of occurrences of a flag).

## Credits

* [José Valim]( and all other creators of [`Elixir`](
* [Kevin K.]( and all other creators of [``](

Brutal picture for the project was made by [Igor Garybaldi](

## Copyright and License

Copyright (c) 2016 Ilya Averyanov

This work is free. You can redistribute it and/or modify it under the
terms of the MIT License. See the [](./ file for more details.

[![Sponsored by FunBox](](