Scala Cookbook

14.10. Using Scala as a Scripting Language

Problem

You want to use Scala as a scripting language on Unix systems, replacing other scripts you’ve written in a Unix shell (Bourne Shell, Bash), Perl, PHP, Ruby, etc.

Solution

Save your Scala code to a text file, making sure the first three lines of the script contain the lines shown, which will execute the script using the scala interpreter:

#!/bin/sh
exec scala "$0" "$@"
!#

println("Hello, world")

To test this, save the code to a file named hello.sh, make it executable, and then run it:

$ chmod +x hello.sh

$ ./hello.sh
Hello, world

As detailed in the next recipe, command-line parameters to the script can be accessed via an args array, which is implicitly made available to you:

#!/bin/sh
exec scala "$0" "$@"
!#

args.foreach(println)

Discussion

Regarding the first three lines of a shell script:

• The #! in the first line is the usual way to start a Unix shell script. It invokes a Unix Bourne shell.

• The exec command is a shell built-in. $0 expands to the name of the shell script, and $@ expands to the positional parameters.

• The !# characters as the third line of the script is how the header section is closed.

A great thing about using Scala in your scripts is that you can use all of its advanced features, such as the ability to create and use classes in your scripts:

#!/bin/sh
exec scala "$0" "$@"
!#

class Person(var firstName: String, var lastName: String) {
  override def toString = firstName + " " + lastName
}

println(new Person("Nacho", "Libre"))

Using ...