Yours first program should be practical...

#!/usr/bin/env ruby1.9.1
# coding: utf-8

if ARGV.empty?
  STDERR.puts "Usage: fajrant hours"
  exit(-1)
end

begin
  hours = Integer(ARGV[0])
rescue ArgumentError => e
  STDERR.puts e.message, "\n", "Usage: fajrant hours"
  exit(-1)
end

(hours * 60).downto(0) do |i|
  puts(format('Minutes left: %10d', i))
  sleep(60)
end

puts "FAJRAAAAAAAAAANT!!"