What does *args mean?

Question

What does args mean, and what is different between it and ARGV if there is a difference?

 def puts_two(*args)
    arg1, arg2 = args
    puts "arg1: #{arg1}, arg2: #{arg2}"
    end

Answer 1

In this case, *args and ARGV have nothing to do with each other. In your example:

def puts_two(*args)
    arg1, arg2 = args
    puts "arg1: #{arg1}, arg2: #{arg2}"
end

*args is just the parameters passed to the method puts_two. The * is the 'splat' operator, which means any number of arguments can be passed to the method and they will be 'splatted' in to an array. So if you called it with:

puts_two('one', 'two', 'three')

args will be an array that looks like ['one', 'two', 'three'].

Notice that in the assignment of the variables arg1 and arg2 only the first 2 elements of the array will be used, so using my example above

arg1, arg2 = ['one', 'two', 'three']

arg1 => 'one'
arg2 => 'two'

ARGV is simply the arguments passed to the ruby script from the command line.

Answer 2

This is referred to as the "splat operator" in Ruby. See the following article for different uses:

The Strange Ruby Splat

In a method definition it basically just gathers all remaining arguments into a single array (note that since Ruby 2.0 there's also the possibility to gather keyword args with something like **kwargs).

Answer 3

* is called splat operator.In *args here * creating an array with all the arguments sent to the method puts_two, and args as a local variable holds the reference to the array. In more clear way - The splat operator is used to handle methods which have a variable parameter list(ie Arraying your arguments).

ARGV contains the arguments passed to your script, one per element.

For example:

$ ruby argf.rb -v glark.txt

In argf.rb file, you will get as below :

ARGF.argv   #=> ["-v", "glark.txt"]

Answer 4

ARGV is a special variable in Ruby. It contains the arguments passed to the script on the command line. For example, if you write the following code in a file called test.rb:

ARGV.each do |a|
    puts a
end

and call it like this

c:\> ruby test.rb one two

will display

one
two

In the code you posted, *args simply indicates that the method accepts a variable number of arguments in an array called args. It could have been called anything you want (following the Ruby naming rules, of course).

So in this case, args is totally unrelated to ARGV.