How to install the Scala debugger CLI.


As the CLI uses the Scala debugger API, you need to have tools.jar available (provided by Oracle's JDK and OpenJDK). This is typically as simple as installing the JDK on your system.

At runtime, the Scala debugger CLI will attempt to load tools.jar from a variety of locations including JDK_HOME, JAVA_HOME, and the system property java.home. If the Scala debugger API has issues loading tools.jar, you should set either JDK_HOME or JAVA_HOME to the path to your JDK.

See the Scala debugger API prerequisites section for more information on finding your JDK path.

Downloading the binary

The Scala debugger CLI has fat jars hosted on Github, built against Scala 2.10, 2.11, and 2.12. You can find a link to the latest release of the CLI here:

The CLI can debug code independently of the version of Scala that it is built against; so, pick whichever binary you prefer.

Verifying it works

  1. Download a binary distribution as described in the earlier section
  2. Start another Java program with -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005
  3. Run the CLI binary via java -jar <YOUR_CLI_BINARY>.jar
  4. Attach to the other Java program via attach 5005
  5. Issue other commands such as listing the threads of the remote JVM via threads