haskellscript

Command line tool for running Haskell scripts with a hashbang.

This tool provides the ability to script in a shell with Haskell (including dependencies) the same way that has been possible with bash scripts or Python.

Examples

Print out JSON constructed with Aeson

https://github.com/seanparsons/haskellscript/blob/master/Example.hs

Lookup weather for your current IP address

https://github.com/seanparsons/haskellscript/blob/master/WeatherExample.hs

Prerequisites

A sandbox capable install of Cabal.

Howto

The script falls into three main parts:

• The hashbang first line:

#!/usr/bin/env haskellscript

• Dependencies (potentially including versions):

--#aeson

• The code:

import Data.Aeson
import Data.ByteString.Lazy hiding (putStrLn, unpack)
import Data.Text
import Data.Text.Encoding
jsonExample = object ["Test" .= True, "Example" .= True]
main = putStrLn $ unpack $ decodeUtf8 $ toStrict $ encode jsonExample

Note that because the dependencies specified are hashed to enable re-use it's worth specifying exact versions across multiple scripts to prevent the version used being quite old after a while.