Turtle.Options

Example usage of this module:

-- options.hs

{-# LANGUAGE OverloadedStrings #-}

import Turtle

parser :: Parser (Text, Int)
parser = (,) <$> optText "name" 'n' "Your first name"
             <*> optInt  "age"  'a' "Your current age"

main = do
    (name, age) <- options "Greeting script" parser
    echo (repr (format ("Hello there, "%s) name))
    echo (repr (format ("You are "%d%" years old") age))

$ ./options --name John --age 42
Hello there, John
You are 42 years old

$ ./options --help
Greeting script

Usage: options (-n|--name NAME) (-a|--age AGE)

Available options:
 -h,--help                Show this help text
 --name NAME              Your first name
 --age AGE                Your current age

See the Turtle.Tutorial module which contains more examples on how to use command-line parsing.

Types

data Parser a :: * -> *

A Parser a is an option parser returning a value of type a.

Instances

Functor Parser

Methods

fmap :: (a -> b) -> Parser a -> Parser b

(<$) :: a -> Parser b -> Parser a

Applicative Parser

Methods

pure :: a -> Parser a

(<*>) :: Parser (a -> b) -> Parser a -> Parser b

liftA2 :: (a -> b -> c) -> Parser a -> Parser b -> Parser c

(*>) :: Parser a -> Parser b -> Parser b

(<*) :: Parser a -> Parser b -> Parser a

Alternative Parser

Methods

empty :: Parser a

(<|>) :: Parser a -> Parser a -> Parser a

some :: Parser a -> Parser [a]

many :: Parser a -> Parser [a]

newtype ArgName

The name of a command-line argument

This is used to infer the long name and metavariable for the command line flag. For example, an ArgName of "name" will create a --name flag with a NAME metavariable

Constructors

ArgName

Fields

• getArgName :: Text

Instances

IsString ArgName

Methods

fromString :: String -> ArgName

newtype CommandName

The name of a sub-command

This is lower-cased to create a sub-command. For example, a CommandName of "Name" will parse name on the command line before parsing the remaining arguments using the command's subparser.

Constructors

CommandName

Fields

• getCommandName :: Text

Instances

IsString CommandName

Methods

fromString :: String -> CommandName

type ShortName = Char

The short one-character abbreviation for a flag (i.e. -n)

newtype Description

A brief description of what your program does

This description will appear in the header of the --help output

Constructors

Description

Fields

• getDescription :: Doc

Instances

IsString Description

Methods

fromString :: String -> Description

newtype HelpMessage

A helpful message explaining what a flag does

This will appear in the --help output

Constructors

HelpMessage

Fields

• getHelpMessage :: Text

Instances

IsString HelpMessage

Methods

fromString :: String -> HelpMessage

Flag-based option parsers

switch :: ArgName -> ShortName -> Optional HelpMessage -> Parser Bool

This parser returns True if the given flag is set and False if the flag is absent

optText :: ArgName -> ShortName -> Optional HelpMessage -> Parser Text

Parse a Text value as a flag-based option

optLine :: ArgName -> ShortName -> Optional HelpMessage -> Parser Line

Parse a Line value as a flag-based option

optInt :: ArgName -> ShortName -> Optional HelpMessage -> Parser Int

Parse an Int as a flag-based option

optInteger :: ArgName -> ShortName -> Optional HelpMessage -> Parser Integer

Parse an Integer as a flag-based option

optDouble :: ArgName -> ShortName -> Optional HelpMessage -> Parser Double

Parse a Double as a flag-based option

optPath :: ArgName -> ShortName -> Optional HelpMessage -> Parser FilePath

Parse a FilePath value as a flag-based option

optRead :: Read a => ArgName -> ShortName -> Optional HelpMessage -> Parser a

Parse any type that implements Read

opt :: (Text -> Maybe a) -> ArgName -> ShortName -> Optional HelpMessage -> Parser a

Build a flag-based option parser for any type by providing a Text-parsing function

Positional argument parsers

argText :: ArgName -> Optional HelpMessage -> Parser Text

Parse a Text as a positional argument

argLine :: ArgName -> Optional HelpMessage -> Parser Line

Parse a Line as a positional argument

argInt :: ArgName -> Optional HelpMessage -> Parser Int

Parse an Int as a positional argument

argInteger :: ArgName -> Optional HelpMessage -> Parser Integer

Parse an Integer as a positional argument

argDouble :: ArgName -> Optional HelpMessage -> Parser Double

Parse a Double as a positional argument

argPath :: ArgName -> Optional HelpMessage -> Parser FilePath

Parse a FilePath as a positional argument

argRead :: Read a => ArgName -> Optional HelpMessage -> Parser a

Parse any type that implements Read as a positional argument

arg :: (Text -> Maybe a) -> ArgName -> Optional HelpMessage -> Parser a

Build a positional argument parser for any type by providing a Text-parsing function

Consume parsers

subcommand :: CommandName -> Description -> Parser a -> Parser a

Create a sub-command that parses CommandName and then parses the rest of the command-line arguments

The sub-command will have its own Description and help text

subcommandGroup :: forall a. Description -> [(CommandName, Description, Parser a)] -> Parser a

Create a named group of sub-commands

options :: MonadIO io => Description -> Parser a -> io a

Parse the given options from the command line