How to use the command 'scala' (with examples)

The ‘scala’ command is a Scala application launcher and interactive interpreter. It can be used to start a REPL (interactive shell), execute Scala scripts and programs, and run single Scala commands in the command-line.

Use case 1: Start a REPL (interactive shell)

Code:

scala

Motivation: Starting a REPL allows you to interactively execute Scala code, making it easy to experiment and test code snippets. It’s an essential tool for learning and exploring the Scala language.

Explanation:

• The command scala starts the interactive Scala interpreter, also known as the Read-Eval-Print Loop (REPL).

Example output:

Welcome to Scala version 2.13.5 (OpenJDK 64-Bit Server VM, Java 11.0.11).
Type in expressions for evaluation. Or try :help.

scala>

Use case 2: Start the interpreter with a dependency in the classpath

Code:

scala -classpath filename.jar command

Motivation: When working with Scala, you often need to use external libraries or dependencies. By specifying a classpath with the -classpath option, you can make those dependencies available to the interpreter.

Explanation:

• The -classpath option specifies the classpath to be used for the Scala interpreter.
• filename.jar represents the path to the external JAR file containing the desired dependencies.
• command represents the Scala code or script to be executed.

Example output:

Hello, Scala!

Use case 3: Execute a Scala script

Code:

scala script.scala

Motivation: With the ‘scala’ command, you can execute Scala scripts directly from the command-line, eliminating the need to compile and run them separately.

Explanation:

• script.scala represents the path to the Scala script file you want to execute.

Example output:

The sum of 3 and 5 is 8.

Use case 4: Execute a .jar program

Code:

scala filename.jar

Motivation: If you have a Scala program packaged as a JAR file, you can directly execute it using the ‘scala’ command without the need for a separate Java command.

Explanation:

• filename.jar represents the path to the JAR file containing the Scala program.

Example output:

Running Scala program...

Use case 5: Execute a single Scala command in the command-line

Code:

scala -e command

Motivation: Sometimes, you may want to quickly execute a single Scala command without entering the interactive shell. The -e option allows you to do just that.

Explanation:

• The -e option specifies that the following argument is a single Scala command to be executed.

Example output:

Hello, Scala!

Conclusion:

The ‘scala’ command is a versatile tool for working with Scala, providing an interactive shell (REPL) for experimentation, the ability to execute scripts and programs, and run single Scala commands from the command-line. By understanding the different use cases and options available, you can leverage the power of Scala effectively.