You may get an error like Parse error processing dependency '30log >= 0.8' if you use luarocks 2.1 or older. In this case, either upgrade to at least luarocks 2.1.1 or install 30log manually, then download the rockspec for argparse, remove the line "30log >= 0.8" and run

$ luarocks install /path/to/argparse/rockspec

Without luarocks

Download /src/argparse.lua file and put it into the directory for libraries or your working directory. Install 30log using luarocks or manually download 30log.lua file from 30log repo.

Tutorial

Creating a parser

The module contains the Parser class. To create an instance, call it or its :new() method.

-- script.lua
local argparse = require "argparse"
local parser = argparse()

parser is now an empty parser which does not recognize any command line arguments or options.

Parsing command line arguments

:parse([cmdline]) method of the Parser class returns a table with processed data from the command line or cmdline array.

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

When executed, this script prints nothing because the parser is empty and no command line arguments were supplied.

$ lua script.lua

Error handling

If the provided command line arguments are not recognized by the parser, it will print an error message and calls os.exit(1).

$ lua script.lua foo

Usage: script.lua [-h]

Error: too many arguments

If halting the program is undesirable, :pparse([cmdline]) method should be used. It returns boolean flag indicating success of parsing and result or error message.

Help option

As the automatically generated usage message states, there is a help option -h added to any parser by default.

When a help option is used, parser will print a help message and call os.exit(0).

$ lua script.lua -h

Usage: script.lua [-h]

Options: 
   -h, --help            Show this help message and exit.

Typo autocorrection

When an option is not recognized by the parser, but there is an option with a similar name, a suggestion is automatically added to the error message.

$ lua script.lua --hepl

Usage: script.lua [-h]

Error: unknown option '--hepl'
Did you mean '--help'?

Configuring parser

Parsers have several fields affecting their behavior. For example, description field sets the text to be displayed in the help message between the usage message and the listings of options and arguments. Another is name, which overwrites the name of the program which is used in the usage message(default value is inferred from command line arguments).

There are several ways to set fields. The first is to call a parser with a table containing some fields.

local parser = argparse() {
   name = "script",
   description = "A testing script. "
}

The second is to chain setter methods of Parser object.

local parser = argparse()
   :name "script"
   :description "A testing script. "

As a special case, name field can be set by calling a parser with a string.

local parser = argparse "script"
   :description "A testing script. "

Adding arguments

Positional arguments can be added using :argument() method. It returns an Argument instance, which can be configured in the same way as Parsers. The name field is required.

parser:argument "input" -- sugar for :argument():name "input"

$ lua script.lua foo

input	foo

The data passed to the argument is stored in the result table at index input because it is the argument's name. The index can be changed using target field.

Setting number of arguments

args field sets how many command line arguments the argument consumes. Its value is interpreted as follows:

Value	Interpretation
Number `N`	Exactly `N` arguments
String `"A-B"`, where `A` and `B` are numbers	From `A` to `B` arguments
String `"N+"`, where `N` is a number	`N` or more arguments
String `"?"`	An optional argument
String `"*"`	Any number of arguments
String `"+"`	At least one argument

If more than one argument can be passed, a table is used to store the data.

parser:argument "pair"
   :args(2)
   :description "A pair of arguments. "
parser:argument "optional"
   :args "?"
   :description "An optional argument. "

$ lua script.lua foo bar

pair	{foo, bar}

$ lua script2.lua foo bar baz

pair	{foo, bar}
optional	baz

Adding options

Options can be added using :option() method. It returns an Option instance, which can be configured in the same way as Parsers. The name field is required. An option can have several aliases, which can be set using aliases field or by continuously calling the Option instance.

parser:option "-f" "--from"

$ lua script.lua --from there
$ lua script.lua --from=there
$ lua script.lua -f there
$ lua script.lua -fthere

from	there

For an option, default index used to store data is the first 'long' alias (an alias starting with two control characters) or just the first alias, without control characters.

Flags

Flags are almost identical to options, except that they don't take an argument by default.

parser:flag "-q" "--quiet"

$ lua script.lua -q

quiet	true

Control characters

The first characters of all aliases of all options of a parser form the set of control characters, used to distinguish options from arguments. Typically the set only consists of a hyphen.

Setting number of arguments

Just as arguments, options can be configured to take several command line arguments.

parser:option "--pair"
   :args(2)
parser:option "--optional"
   :args "?"

$ lua script3.lua --pair foo bar

pair	{foo, bar}

$ lua script3.lua --pair foo bar --optional

pair	{foo, bar}
optional	{}

$ lua script3.lua --optional=baz

optional	{baz}

Note that the data passed to optional option is stored in an array. That is necessary to distinguish whether the option was invoked without an argument or it was not invoked at all.

Setting number of invocations

For options, it is possible to control how many times they can be used. argparse uses count field to set how many times an option can be invoked. The value of the field is interpreted in the same way args is.

parser:option "-e" "--exclude"
   :count "*"

$ lua script.lua -eFOO -eBAR

exclude	{FOO, BAR}

If an option can be used more than once and it can consume more than one argument, the data is stored as an array of invocations, each being an array of arguments.

As a special case, if an option can be used more than once and it consumes no arguments(e.g. it's a flag), than the number of invocations is stored in associated field of the result table.

parser:flag "-v" "--verbose"
   :count "0-2"
   :target "verbosity"
   :description [[Sets verbosity level. 
-v: Report all warning. 
-vv: Report all debugging information. ]]

$ lua script.lua -vv

verbosity	2

Commands

Default values

Converters

Actions

Documentation

Documentation is not available in the doc directory and online. If argparse was installed using luarocks 2.1.2 or later, it can not be viewed using luarocks doc argparse command.

Testing

argparse comes with a testing suite located in spec directory. busted is required for testing, it can be installed using luarocks. Run the tests using busted spec command from the argparse folder.