The dotenv package

[ Tags: configuration, library, mit, program ] [ Propose Tags ]

In most applications, configuration should be separated from code. While it usually works well to keep configuration in the environment, there are cases where you may want to store configuration in a file outside of version control.

Dotenv files have become popular for storing configuration, especially in development and test environments. In Ruby, Python and Javascript there are libraries to facilitate loading of configuration options from configuration files. This library loads configuration to environment variables for programs written in Haskell.

To use, call loadFile from your application:

import Configuration.Dotenv
loadFile False "/my/dotenvfile"

This package also includes an executable that can be used to inspect the results of applying one or more Dotenv files to the environment, or for invoking your executables with an environment after one or more Dotenv files is applied.

See the Github page for more information on this package.


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Properties

Versions 0.1.0.0, 0.1.0.1, 0.1.0.2, 0.1.0.3, 0.1.0.4, 0.1.0.5, 0.1.0.6, 0.1.0.7, 0.1.0.8, 0.1.0.9, 0.2.0.0, 0.3.0.0, 0.3.0.1, 0.3.0.2, 0.3.0.3, 0.3.1.0, 0.3.2.0, 0.3.3.0, 0.3.4.0, 0.4.0.0, 0.5.0.0, 0.5.0.1, 0.5.0.2, 0.5.1.0 (info)
Change log CHANGELOG.md
Dependencies base (>=4.7 && <5.0), base-compat (>=0.4), dotenv, exceptions (==0.8.*), megaparsec (>=6.0 && <7.0), optparse-applicative (>=0.11 && <0.15), process (>=1.4.3.0), text, transformers (>=0.4 && <0.6), void (==0.7.*) [details]
License MIT
Copyright 2015-2017 Stack Builders Inc.
Author Justin Leitgeb
Maintainer hackage@stackbuilders.com
Category Configuration
Home page https://github.com/stackbuilders/dotenv-hs
Bug tracker https://github.com/stackbuilders/dotenv-hs/issues
Source repository head: git clone git@github.com:stackbuilders/dotenv-hs.git
Uploaded Thu Oct 5 16:23:24 UTC 2017 by camm
Distributions LTSHaskell:0.3.4.0, NixOS:0.5.0.1, Stackage:0.5.1.0, Tumbleweed:0.3.4.0
Executables dotenv
Downloads 3147 total (203 in the last 30 days)
Rating 0.0 (0 ratings) [clear rating]
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Status Docs available [build log]
Last success reported on 2017-10-05 [all 1 reports]
Hackage Matrix CI

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Flags

NameDescriptionDefaultType
dev

Turn on development settings.

DisabledManual

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

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Maintainer's Corner

For package maintainers and hackage trustees


Readme for dotenv-0.5.1.0

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Build Status Hackage

Dotenv files for Haskell

In most applications, configuration should be separated from code. While it usually works well to keep configuration in the environment, there are cases where you may want to store configuration in a file outside of version control.

"Dotenv" files have become popular for storing configuration, especially in development and test environments. In Ruby, Python and Javascript there are libraries to facilitate loading of configuration options from configuration files. This library loads configuration to environment variables for programs written in Haskell.

Installation

In most cases you will just add dotenv to your cabal file. You can also install the library and executable by invoking stack install dotenv.

Usage

Set configuration variables in a file following the format below:

S3_BUCKET=YOURS3BUCKET
SECRET_KEY=YOURSECRETKEYGOESHERE

Then, calling Dotenv.load from your Haskell program reads the above settings into the environment:

import qualified Configuration.Dotenv as Dotenv
Dotenv.loadFile False "/path/to/your/file"

After calling Dotenv.load, you are able to read the values set in your environment using standard functions from System.Environment such as lookupEnv and getEnv.

NOTE: Empty environment variables

If you need to have empty environment variables in your configuration, you can use something like the code below:

fromMaybe "" <$> lookupEnv "ENV_VAR"

Currently, dotenv-hs doesn't allow you to set empty environment variables, because of setEnv from our System.Environment. This is bug reported in GHC ticket. We have had many dicussions about this. Fortunately, there is already some work for this issue in GHC Phabricator.

Variable substitution

In order to use compound env vars use the following sintax within your env vars ${your_env_var}. For instance:

DATABASE=postgres://${USER}@localhost/database

Running it on the CLI:

$ dotenv "echo $DATABASE"
postgres://myusername@localhost/database

Command substitution

In order to use the standard output of a command in your env vars use the following sintax $(your_command). For instance:

DATABASE=postgres://$(whoami)@localhost/database

Running it on the CLI:

$ dotenv "echo $DATABASE"
postgres://myusername@localhost/database

Configuration

The first argument to loadFile specifies whether you want to override system settings. False means Dotenv will respect already-defined variables, and True means Dotenv will overwrite already-defined variables.

Advanced Dotenv File Syntax

You can add comments to your Dotenv file, on separate lines or after values. Values can be wrapped in single or double quotes. Multi-line values can be specified by wrapping the value in double-quotes, and using the "\n" character to represent newlines.

The spec file is the best place to understand the nuances of Dotenv file parsing.

Command-Line Usage

You can call dotenv from the command line in order to load settings from one or more dotenv file before invoking an executable:

$ dotenv -f mydotenvfile myprogram

The -f flag is optional, by default it looks for the .env file in the current working directory.

$ dotenv myprogram

Aditionally you can pass arguments and flags to the program passed to Dotenv:

$ dotenv -f mydotenvfile myprogram -- --myflag myargument

or:

$ dotenv -f mydotenvfile "myprogram --myflag myargument"

Also, you can use a --example flag to use dotenv-safe functionality so that you can have a list of strict envs that should be defined in the environment or in your dotenv files before the execution of your program. For instance:

$ cat .env.example
DOTENV=
FOO=
BAR=

$ cat .env
DOTENV=123

$ echo $FOO
123

This will fail:

$ dotenv -f .env --example .env.example "myprogram --myflag myargument"
> dotenv: Missing env vars! Please, check (this/these) var(s) (is/are) set: BAR

This will succeed:

$ export BAR=123 # Or you can do something like: "echo 'BAR=123' >> .env"
$ dotenv -f .env --example .env.example "myprogram --myflag myargument"

Hint: The env program in most Unix-like environments prints out the current environment settings. By invoking the program env in place of myprogram above you can see what the environment will look like after evaluating multiple Dotenv files.

Author

Justin Leitgeb

License

MIT

Copyright

(C) 2015-2017 Stack Builders Inc.