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.