Covert octal number to decimal number with Ruby

octal_to_decimal.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

# Usage: ruby octal_to_decimal.rb <octal_number>

# Covert octal number to decimal number
def octal_to_decimal n
    exponent = 0
    result = 0
    n = n.to_s
    (n.length - 1).downto(0) do |i|
        result += n[i].to_i * pow(8, exponent)
        exponent += 1
    end
    result
end

# The pow() function returns the result of the first argument raised to the power of the second argument.
def pow(base, exponent)
    if (exponent == 0) 
        return 1
    end
    return base * pow(base, exponent - 1)
end

puts octal_to_decimal(ARGV[0])