gistfile1.txt

➜  triangle_lulz  ruby triangle.rb
Enter base size 
10
Triangle of base size 10:
*
**
***
****
*****
******
*******
********
*********
**********
***********
************
➜  triangle_lulz  

t.rb

puts "Enter base size "
base = gets.chomp.to_i

puts "Triangle of base size #{base}:"

[*0..base].each do |col|
  print "*\n"
  [*0..col].each do
    print "*"
  end
end
print "*\n"