DotEnv.jl is a lightweight package that loads environment variables from .env files into =ENV=. Storing configuration in the environment is based on The Twelve-Factor App methodology.

Please don’t store secrets in dotenv files, and if you must at least ensure the dotenv file(s) are listed in .gitignore.

using DotEnv
DotEnv.load!()

Create a .env file in your project. You can add environment-specific variables using the rule NAME=VALUE. For example:

#.env file
DB_HOST=127.0.0.1
DB_USER=john
DB_PASS=42

When DotEnv.load!() is called, all variables declared in the .env file that are not already present in ENV are loaded into it.

julia> ENV["DB_PASS"]
"42"

To load variables from dotenv files even when they are already present in the environment dictionary, pass override = true to DotEnv.load!.

DotEnv.unload!() will reverse the changes of DotEnv.load!().

This works even when the environment is modified incrementally (i.e. loading files one at a time).

config reads a dotenv file, parse the content, applies variable expansion, but does not modify the base environment dictionary.

julia> using DotEnv

julia> cfg = DotEnv.config() # defaults to reading `.env`
DotEnv.EnvOverlay{Base.EnvDict} with 3 entries:
  "DB_PASS" => "42"
  "DB_HOST" => "127.0.0.1"
  "DB_USER" => "john"

DotEnv.parse accepts a String or an IOBuffer (Any value that can be converted into String), and it will return a Dict with the parsed keys and values.

julia> using DotEnv

julia> DotEnv.parse("FOO=bar\nBAR=baz")
Dict{String, String} with 2 entries:
  "FOO" => "bar"
  "BAR" => "baz"

1. Leading whitespace is ignored
2. Empty lines, and lines starting with # are skipped
3. export prefixes are ignored (e.g. export FOO=bar)
4. Empty assignments are regarded as the empty string(EMPTY= becomes "EMPTY" => "")
5. Keys and values are separated by === or :, and any amount of whitespace
6. All values are strings, but can be quoted with single (') or double quotes (")
7. Quotes of the same type may occur within quoted values, but must be escaped with \
8. Inline comments are started with a # outside of a quoted value
9. Inside double quoted values, \n newlines are expanded, allowing for multiline values
10. Extra spaces are removed from both ends of an unquoted value (e.g. FOO some value = becomes "FOO" => "some value")
11. Variable expansion occurs within unquoted and double-quoted values. $NAME, ${NAME}, and ${NAME:-default} expansions are all supported.
12. Malformed lines are silently skipped