How can I take a specific number of lines of input in Ruby?

Question

I am taking inputs in Ruby like this:

lines = STDIN.readlines.map{|x| x.strip.to_i}.sort

This takes input from the command prompt, but I want to take input a specific number of times. Suppose my number of test cases is 3, how can I stop it after 3 lines of input?

Answer 1

lines = []
3.times do
  lines << STDIN.readline.strip.to_i
end
lines.sort

---

EDIT:

If you are saying that you want it to accept an arbitrary number of inputs, you have a couple options: The simplest is to first input how many lines of input you have, like this:

num_lines = STDIN.readline.strip.to_i
lines = []
num_lines.times do
  lines << STDIN.readline.strip.to_i
end
lines.sort

Or, if you don't know how many lines to expect, you have to have some way of signifying that the data is complete. For example, if you want to have an empty line mean the end of the data:

lines = []
STDIN.each_line do |line|
  line.strip!
  break if line == ''
  lines << line.to_i
end
lines.sort

By the way, when the program is paused while awaiting input, this is not called an "infinite loop". It is "blocking" or simply "waiting for input".

Answer 2

One line of code...

This will take only the number of lines you want to use - the desired count is in variable @requested_count:

lines = STDIN.readlines.values_at(0..@requested_count - 1).map{|x| x.strip.to_i}.sort

Answer 3

A variation on the previous answers:

lines = []
1.upto(3) do
  lines << STDIN.readline.strip.to_i
end
puts lines.sort

Answer 4

Why not use gets?

lines = []
1.upto(3) do
  lines << gets.to_i
end

puts lines.sort