ghc-envparse

Here's a simple example of a program that uses 'envparse''s parser:
' module Main (main) where
import Control.Monad (unless) import Env
data Hello = Hello { name :: String, quiet :: Bool }
hello :: IO Hello hello = Env.parse (header "envparse example") $   Hello
<$> var (str <=< nonempty) "NAME" (help "Target for the greeting") &#x20; <*>
switch "QUIET" (help "Whether to actually print the greeting") &#x20; main ::
IO () main = do &#x20; Hello &#x7b;name, quiet&#x7d; <- hello &#x20; unless
quiet $ &#x20; putStrLn ("Hello, " ++ name ++ "!") '
The 'NAME' environment variable is mandatory and contains the name of the
person to greet. 'QUIET', on the other hand, is an optional boolean flag, false
by default, that decides whether the greeting should be silent.
If the 'NAME' variable is undefined in the environment then running the program
will result in the following help text:
' envparse example &#x20; Available environment variables: &#x20; &#x20; NAME
Target for the greeting &#x20; QUIET Whether to actually print the &#x20;
greeting &#x20; Parsing errors: &#x20; &#x20; NAME is unset '.

          

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License: BSD-3-Clause
URL: https://hackage.haskell.org/package/envparse