https://github.com/meowgorithm/mr-env

A simple way to read environment variables in Haskell
https://github.com/meowgorithm/mr-env

environment-variables haskell

Last synced: 2 months ago
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A simple way to read environment variables in Haskell

• Host: GitHub
• URL: https://github.com/meowgorithm/mr-env
• Owner: meowgorithm
• License: mit
• Created: 2020-03-15T01:29:31.000Z (almost 5 years ago)
• Default Branch: master
• Last Pushed: 2022-11-06T01:21:13.000Z (about 2 years ago)
• Last Synced: 2024-09-29T17:41:41.077Z (3 months ago)
• Topics: environment-variables, haskell
• Language: Haskell
• Homepage: https://hackage.haskell.org/package/mr-env-0.1.0.0
• Size: 64.5 KB
• Stars: 2
• Watchers: 4
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: ChangeLog.md
  • License: LICENSE

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README

        
# Mr. Env

![build][action-badge] [![Hackage][hackage-shield]][hackage]

[action-badge]: https://github.com/meowgorithm/mr-env/workflows/build/badge.svg

[hackage]: http://hackage.haskell.org/package/mr-env

[hackage-shield]: https://img.shields.io/hackage/v/mr-env.svg?style=flat&color=blueviolet

A simple way to read environment variables in Haskell.

```haskell

-- Read environment variables, with defaults

host <- envAsString "HOST" "localhost"

port <- envAsInt "PORT" 8000

```

## Simple Example

Read environment variables with `do` notation:

```haskell

import System.Environment.MrEnv ( envAsBool, envAsInt, envAsInteger, envAsString )

main :: IO ()

main = do

    -- Get a string, with a fallback value if nothing is set.

    host <- envAsString "HOST" "localhost"

    -- Get an int. If you need an integer instead you could also use envAsInteger.

    port <- envAsInt "PORT" 8000

    -- Get a boolean. Here we're expecting the environment variable to read

    -- something along the lines of "true", "TRUE", "True", "truE" and so on.

    debug <- envAsBool "DEBUG" False

    putStrLn $

        "Let's connect to "

        ++ host

        ++ " on port "

        ++ show port

        ++ ". Debug mode is "

        ++ if debug then "on" else "off"

        ++ "."

```

## Fancy Example

Read environment variables into a record:

```haskell

import System.Environment.MrEnv ( envAsBool, envAsInt, envAsInteger, envAsString )

data Config =

    Config { host  :: String

           , port  :: Int

           , debug :: Bool

           }

getConfig :: IO Config

getConfig = Config

    <$> envAsString "HOST" "localhost"

    <*> envAsInt "PORT" 8000

    <*> envAsBool "DEBUG" False

main :: IO ()

main =

    getConfig >>= \conf ->

        putStrLn $

            "Let's connect to "

            ++ host conf

            ++ " on port "

            ++ show $ port conf

            ++ ". Debug mode is "

            ++ if debug conf then "on" else "off"

            ++ "."

```

We suggest pronouncing `<*>` _[brackety-splat][1]_ (as

opposed to _ap_). In that vein, `<$>` is _brackety-cash._

[1]: https://www.reddit.com/r/haskell/comments/241jcm/how_do_you_say/

## Authors

* [Christian Rocha](https://github.com/meowgorithm)

* [Sam Raker](https://github.com/swizzard)

## License

MIT