In Java, reading environment variables is done with System.getenv().
Is there a way to do this in Scala?
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7 Answers
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.
3 Comments
Cristian Vrabie
It's probably better practice to use
sys.env.get("VARIABLE") which will give you an Option[String] rather than throw an error if that variable is missing.
paradigmatic
@CristianVrabie I would prefer it also, in most cases. But
sys.env is just a Map. You can whatever method is appropriate for you.
Josh Peak
sys.env.getOrElse("VARIABLE", "default value") was also helpful in my case where the environment variable may not be defined.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" )
1 Comment
ppopoff
I would also prefer Properties. It allows to retrieve Optionals, and has names for commonly used properties.
Same way:
scala> System.getenv("HOME")
res0: java.lang.String = /Users/dhg
1 Comment
summerbulb
Now that I use Scala on a daily basis, I must move the accepted answer to @paradigmatic's answer. It uses Scala API and if used as suggested in the comments can return an Option.
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.
Comments
If Lightbend's configuration library is used (by default in Play2 and Akka) then you can use
foo = "default value"
foo = ${?VAR_NAME}
syntax to override foo if an environment variable VAR_NAME exist. More details in https://github.com/typesafehub/config#optional-system-or-env-variable-overrides
Comments
To print all environment variables, you can use
System.getenv.forEach((name, value) => println(s"$name: $value"))
5 Comments
thundergolfer
error: missing parameter type on the args if you just copy-paste this.
Matthias Braun
@thundergolfer: I currently don't have Scala installed on my machine. Did you figure out what was missing?
Roland Weber
After changing the parameters to
(name: String, value: String), I'm getting error: type mismatch; found : (String, String) => Unit required: java.util.function.BiConsumer[_ >: String, _ >: String].Roland Weber
Here's something that works, but requires an import: alvinalexander.com/scala/…
gareth stokes
sys.env.foreach(tuple => println(s"$tuple")) is not as elegant but seems to get the job done.You can use sys.props.getOrElse("key", "default") for Java systems properties.
package scala
object sys {
/** A bidirectional, mutable Map representing the current system Properties.
*
* @return a SystemProperties.
* @see [[scala.sys.SystemProperties]]
*/
def props: SystemProperties = new SystemProperties
/** An immutable Map representing the current system environment.
*
* @return a Map containing the system environment variables.
*/
def env: immutable.Map[String, String] = immutable.Map(System.getenv().asScala.toSeq: _*)
