Getting started with the Scala REPL (command-line shell)

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 14.1, “How to get started with the Scala REPL.”

Back to top


You want to get started using the Scala REPL, including understanding some of its basic features, such as tab completion, starting the REPL with different options, and dealing with errors.

Back to top


To start the Scala REPL, type scala at your operating system command line:

Table of Contents

  1. Problem
  2. Solution
Back to top

Scala SBT: How to “re-run with -deprecation” (or -feature)

Scala FAQ: When compiling a Scala application with SBT, I get warning messages like these:

$ sbt compile

[warn] there were 6 deprecation warnings; re-run with -deprecation for details
[warn] there were 4 feature warnings; re-run with -feature for details

How do I ’re-run with -deprecation’ or ’re-run with -feature’?

Scala REPL: There were deprecation warnings, re-run with -deprecation

Whenever I used to get the Scala REPL warning message, "There were deprecation warnings, re-run with -deprecation", I used to have to restart the REPL with the -deprecation flag to see the warning message, like this:

$ scala -deprecation

That works, but sadly, you had to lose your entire REPL session to run it.

Use :warnings

Thanks to the Scala gods, this is no longer necessary in Scala 2.10 (and newer). Now, when you get the REPL deprecation warning message, like this: