Ruby equivalent to Python __main__ [duplicate]

This question already has answers here: `if __name__ == '__main__&#开发者_StackOverflow中文版39;` equivalent in Ruby (3 answers) Closed 6 years ago.

If in a ruby file I define a function like so:

def tell_the_truth()
    puts "truth"
end

is there an equivalent to python's main?

if __name__ == "__main__":
    tell_the_truth()

Is it to simply call the function inside the file?

tell_the_truth

---

I believe this will work:

if __FILE__ == $0
    tell_the_truth()
end

---

if __FILE__ == $PROGRAM_NAME
    tell_the_truth()
end