args

How to access command-line arguments in Scala shell scripts

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 14.11, “How to access command-line arguments in a Scala shell script.”

Problem

You want to access the command-line arguments from your Scala shell script.

Solution

Use the same script syntax as shown in Recipe 14.8, “Generating Documentation with scaladoc”, and then access the command-line arguments using args, which is a List[String]` that is implicitly made available:

Processing Scala command-line arguments with Argot, and passing command-line arguments through SBT

Argot is the name of a Scala library that lets you read command-line options/arguments from a Scala application. (Presumably it will work with Java and other JVM-based languages as well.)

I’m trying to use Argot with an application of mine named Cato, and when I had problems getting Argot to work -- and then needed to pass command-line arguments to my application through SBT -- I decided to write this quick little test code and article.

How to read Scala command line arguments

Scala command line FAQ: How do I read command line arguments (args) in a Scala shell script?

If your Scala shell script is very short, and you're not using an object or class declaration -- i.e., you have no main method -- you can access the script's command line arguments through the default args array, which is made available to you by Scala.

For instance, you can create a one-line Scala script named hello.scala like this:

Ruby command line arguments

Ruby FAQ: How do I read command line arguments in a Ruby script (Ruby command line args)?

To read command line args in a Ruby script, use the special Ruby array ARGV to get the information you need. Here are a few examples.

1) Getting the number of command line args

To get the number of command line arguments passed in to your Ruby script, check ARGV.length, like this:

Java sound: A command line Java program to play a sound file (in headless mode)

As part of my ongoing HAL 9000 voice obsession, I downloaded a bunch of "HAL 9000" sound files last night. But, when you double-click a sound file on Mac OS X, it automatically plays through iTunes, which is good for some things, but bad for what I wanted to do. So, I wrote a quick little "Java sound" program to read the name of a sound file from the command line, and then play the sound file.

How to prompt and read user input in a Bash shell script

Unix/Linux bash shell script FAQ: How do I prompt a user for input from a shell script (Bash shell script), and then read the input the user provides?

Answer: I usually use the shell script "read" function to read input from a shell script. Here are two slightly different versions of the same shell script. This first version prompts the user for input only once, and then dies if the user doesn't give a correst Y/N answer:

Ruby - Variable length argument lists with Ruby

Ruby FAQ: How do I create a variable length argument list in a Ruby method?

One thing I really dig about Ruby is that I can create methods and functions that support variable-length argument lists. It's not something you need all the time, but it sure is nice to have it when you need it.

Here's how you create and then call a Ruby function/method that can take a variable number of arguments: