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 clap.rs 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.
Add optimus to your list of dependencies in mix.exs:
def deps do
[
{:optimus, "~> 0.2"}
]
endLet'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
Optimus.new!(
name: "statcalc",
description: "Statistic metrics calculator",
version: "1.2.3",
author: "John Smith [email protected]",
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
end
end,
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
end
end,
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
end
end(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:
>./statcalc
The following errors occurred:
- missing required arguments: INPUT_FILE
- missing required options: --from(-f), --to(-t)
Try
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
statcalcwith--helpflag 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 [email protected]
Utility for calculating statistic metrics of values read from a file for a certain period of time
USAGE:
statcalc [--print-header] --from DATE_FROM --to DATE_TO INPUT_FILE [OUTPUT_FILE]
statcalc --version
statcalc --help
statcalc help subcommand
ARGS:
INPUT_FILE File with raw data
OUTPUT_FILE File to write statistics to
FLAGS:
-h, --print-header Specifies whether to print header before the
outputs
OPTIONS:
-f, --from Start date for the period
-t, --to End date for the period (default: 2017-12-20)
SUBCOMMANDS:
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 (
--versionandhelp 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
%Optimus.ParseResult{
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:
unknownlist is always empty if we setallow_unknown_args: falsefor our (sub)command;- values in
args,flagsandoptionsmaps are kept under keys specified in configuration; - for options with
multiple: truethe value is a list; - for flags without
multiple: truethe value is a boolean; - for flags with
multiple: truethe value is an integer (representing the number of occurrences of a flag).
- José Valim and all other creators of
Elixir - Kevin K. and all other creators of
clap.rs
Brutal picture for the project was made by Igor Garybaldi.
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 LICENSE.md file for more details.
