Adding and configuring arguments¶
Positional arguments can be added using :argument(name, description, default, convert, args)
method. It returns an Argument instance, which can be configured in the same way as Parsers. The name
property is required.
This and the following examples show contents of the result table returned by parser:parse() when the script is executed with given command-line arguments.
1 | parser:argument "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
property.
Setting number of consumed arguments¶
args
property 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 consumed, a table is used to store the data.
1 2 3 4 | parser:argument("pair", "A pair of arguments.")
:args(2)
parser:argument("optional", "An optional argument.")
:args "?"
|
$ lua script.lua foo bar
{
pair = {"foo", "bar"}
}
$ lua script.lua foo bar baz
{
pair = {"foo", "bar"},
optional = "baz"
}
Setting argument choices¶
The choices
property can be used to restrict an argument to a set of choices. Its value is an array of string choices.
1 2 | parser:argument "direction"
:choices {"north", "south", "east", "west"}
|
$ lua script.lua foo
Usage: script.lua [-h] {north,south,east,west}
Error: argument 'direction' must be one of 'north', 'south', 'east', 'west'