This is a cheat-sheet of handy Scala-CLI commands. I have written a blog post about Scala-CLI and how it can make it easy for Scala beginners.
For installation of the Scala-CLI, please take a look at the official documentation. If you already use Coursier, you can use it to install Scala-CLI:
cs install scala-cli
| Command | Description |
|---|---|
| scala-cli Hello.scala | Compiles and runs Hello.scala file |
| scala-cli compile Hello.scala | Compiles Hello.scala file without running |
| scala-cli run Hello.scala | Runs Hello.scala file (same as scala-cli Hello.scala) |
| scala-cli setup-ide . | Prepares the config files needed to open in IDE. Now we can open in IntelliJ or VSCode Metals |
| scala-cli -S 2.13.10 Hello.scala | Compiles and runs Hello.scala using the compiler version 2.13.10. Scala-CLI automatically downloads relevant version |
| scala-cli fmt Hello.scala | Formats Hello.scala using scalafmt |
| scala-cli clean . | Delete the .scala-build and clean contents of .bsp directories that contains compiled sources. Notice that, this deletes IDE config, so you need to do setup-ide again |
| scala-cli --power package Hello.scala -o app | Creates an executable application with name app for the file Hello.scala |
| scala-cli --jvm zulu:21.0.0 Hello.scala | Uses Zulu JDK 21 to execute Hello.scala. It downloads the JDK automatically |
| scala-cli --jvm 19 Hello.scala | Uses Open JDK 19 to execute Hello.scala |
| scala-cli repl | Starts a Scala REPL with the default Scala Version |
| scala-cli repl -S 2.13.12 | Starts the Scala REPL with the specific version |
Directives are special statements in Scala-CLI. They are added as comments with a special syntax as part of the Scala code.
Directives starts with the syntax //>. Scala-CLI differentiates them from normal comments and process them in a special way.
Here are some of the useful directives:
| Directive | Description |
|---|---|
| //> using scala 3 | This informs Scala-CLI that the following code is written in Scala 3.x version (not 2.x). Hence it uses latest Scala 3 for the code compilation even though local version of Scala is something else |
| //> using scala 3.lts | Uses the LTS version of Scala (e.g. At the moment 3.3.x is the LTS. Eventhough 3.4 is released, this directive uses the LTS 3.3.x version) |
| //> using scala "2.13.12" | Uses the specific version of Scala for the compilation |
| //> using jvm "19" | Scala-CLI uses JVM 19 (adopt open jdk by default) for compilation and execution |
| //> using jvm "zulu:21.0.0" | Uses the specific version of the JDK |
| //> using dep com.lihaoyi::os-lib:0.9.1 | Downloads and brings the os-lib library to the scope so that we can use it |
| //> using javaOpt -Xmx2g | Sets Java Option for the file |
| //> using option -Xfatal-warnings | Sets Scala Compiler Options |
| //> using toolkit default | To use the default version scala toolkit. Before v1.1.1, it was using 'latest' instead of 'default' |