Your First Elixir Script

Elixir gives you two ways to run code: compiled projects managed by mix, and standalone scripts you run directly with the elixir command. For learning and quick experiments, scripts are the faster path — no project scaffolding required.

.ex vs .exs

Elixir source files come in two flavors:

• .ex files are meant to be compiled — typically part of a mix project, producing bytecode that's cached and loaded quickly.
• .exs files are scripts — interpreted fresh every time, no compilation step, ideal for one-off code and tests.

For your first program, .exs is the right choice.

Writing the script

Create a file named hello.exs:

IO.puts("Hello from Elixir!")

name = "World"
IO.puts("Hello, #{name}!")

numbers = [1, 2, 3, 4, 5]
sum = Enum.sum(numbers)
IO.puts("The sum of #{inspect(numbers)} is #{sum}.")

A few things worth noticing already, even before later lessons formalize them: IO.puts/1 prints a line to standard output, #{} interpolates a value into a string, and Enum.sum/1 is a function from Elixir's standard library that reduces a list to a single number.

Running it

elixir hello.exs

No compile step, no build artifacts — the elixir command reads the file top to bottom and executes it directly.

Defining and using a module in a script

Even a quick script can define a module, which is how Elixir organizes related functions:

defmodule MathHelpers do
  def square(n) do
    n * n
  end

  def is_even?(n) do
    rem(n, 2) == 0
  end
end

IO.puts(MathHelpers.square(6))
IO.puts(MathHelpers.is_even?(6))

Functions ending in ? are a naming convention (not a language rule) for functions that return a boolean — is_even?/1 reads naturally in an if later on, exactly the way Enum.empty?/1 or String.contains?/2 do in the standard library.

Passing arguments from the command line

Scripts can read arguments via System.argv/0:

# greet.exs
[name | _rest] = System.argv()
IO.puts("Hey there, #{name}!")

elixir greet.exs Alice
# => Hey there, Alice!

That [name | _rest] = System.argv() line is your first taste of pattern matching — destructuring a list into its first element and "everything else." The next section of this course covers exactly what's happening there and why it's one of Elixir's most useful features.

From here on, most lessons in this course will show snippets you can drop straight into a .exs file and run with elixir filename.exs to see the output for yourself — doing that as you go is the fastest way to build real intuition for the language.