-- script.lua
local argparse = require "argparse"

local parser = argparse:new()
parser:argument "input"
parser:option "-o" "--output"

local args = parser:parse()
for k, v in pairs(args) do
   print(k, v)
end

Does it work?

$ lua script.lua -o out.txt in.txt

input	in.txt
output	out.txt

There are several ways to pass options.

$ lua script.lua --output out.txt in.txt
$ lua script.lua in.txt --output=out.txt
$ lua script.lua in.txt -oout.txt

Does it have help?

$ lua script.lua --help

Usage: test.lua [-o <output>] [-h] <input>

Arguments: 
   input

Options: 
   -o <output>, --output <output>
   -h, --help            Show this help message and exit.

What if we do something wrong?

$ lua script.lua foo bar

Usage: test.lua [-o <output>] [-h] <input>

Error: too many arguments

What if we make a typo?

$ lua script.lua in.txt --outptu out.txt

Usage: test.lua [-o <output>] [-h] <input>

Error: unknown option '--outptu'
Did you mean '--output'?

##Features

Declarative and classic interfaces.

Declarative:

parser:argument "input"
   :description "Path to input file. "
   :convert(io.open)
parser:option "-v" "--verbose"
   :description "Sets logging level. "
   :count "*"

Classic:

parser:argument("input", {
   description = "Path to input file. ",
   convert = io.open
})
parser:option("-v", "--verbose", {
   description  = "Sets logging level. ",
   count = "*"
})

Parses:
- Short options(e.g. -q);
- Combined short options(e.g. -zx);
- Short options combined with arguments(e.g. -I/usr/local/include);
- Long options(e.g. --quiet);
- Long options with arguments(e.g. --from there);
- GNU-style long options with arguments(e.g. --from=there).
Supports named arguments consuming several arguments.

Supports options and flags which can be invoked several times, consuming several arguments.

parser:option "-p" "--pair"
   :count "*"
   :args(2)

parser:flag "-v" "--verbose"
   :count "*"

local args = parser:parse{"--pair", "Alice", "Bob", "-p", "Emma", "John", "-vvv"}
-- args = {
--    pair = {
--       {"Alice", "Bob"},
--       {"Emma", "John"}
--    },
--    verbose = 3
-- }

Supports default values and automatic conversions for arguments.
Automatically generates error, usage and help messages.
Supports commands(e.g. in git CLI add, commit, push, etc. are commands). Each command has its own set of options and arguments.

Automatically generates hints on typos.

parser:option "-f" "--from"
parser:command "install"

parser:parse{"--form", "there"}
-- Error: unknown option '--form'
-- Did you mean '--from'?

parser:parse{"isntall"}
-- Error: unknown command 'isntall'
-- Did you mean 'install'?