How to read environment variables in Scala

Question

Since Scala 2.9 you can use sys.env for the same effect:

scala> sys.env("HOME")
res0: String = /home/paradigmatic

I think is nice to use the Scala API instead of Java. There are currently several project to compile Scala to other platforms than JVM (.NET, javascript, native, etc.) Reducing the dependencies on Java API, will make your code more portable.

There is an object:

scala.util.Properties

this has a collection of methods that can be used to get environment info, including

scala.util.Properties.envOrElse("HOME", "/myhome" )

Same way:

scala> System.getenv("HOME")
res0: java.lang.String = /Users/dhg

Using directly a default with getOrElse over the sys.env Map (val myenv: Map[String, String] = sys.env):

sys.env.getOrElse(envVariable, defaultValue)

You get the content of the envVariable or, if it does not exist, the defaultValue.

If Lightbend's configuration library is used (by default in Play2 and Akka) then you can use

foo = "default value" foo = ${?VAR_NAME}

syntax to override foo if an environment variable VAR_NAME exist. More details in https://github.com/typesafehub/config#optional-system-or-env-variable-overrides