A small Ruby program that returns the value of given position in a Fibonacci sequence.

main.rb

# ask the user what position
puts "What position of a Fibonacci sequence would you like to see the value of? (Ex: position 6 = 8)"

# method for returning the value of a position in a Fibonacci sequence
def fibo_it(num)
    num <= 1 ? num : fibo_it(num - 2) + fibo_it(num - 1)
end

# get the user input and convert to integer
pos = gets.chomp.to_i

# verify the user input is greater than 1 and not a string "abc"
if pos > 1
    # get the value returned by method fibo_it(num)
    val = fibo_it(pos)
    # output pos and val to the user
    puts "The value of position #{pos} in the sequence is #{val}."
else
    # output error
    puts "Position must be an integer and greater than 1"
end