Simple progress bar script without Gem using Ruby.

progress_bar.rb

#!/usr/bin/env ruby

progress = 'Progress ['
1000.times do |i|

# i is number from 0-999
j = i + 1

  # add 1 percent every 10 times
  if j % 10 == 0
    progress << "="
    # move the cursor to the beginning of the line with \r
    print "\r"
    # puts add \n to the end of string, use print instead
    print progress + " #{j / 10} %"

    # force the output to appear immediately when using print
    # by default when \n is printed to the standard output, the buffer is flushed. 
    $stdout.flush
    sleep 0.05
  end
end
puts "\nDone!"

For anyone that tries this with a number other than 1000 I think that this might make things a little more clear:

progress = 'Progress ['
iteration_count = 1000
iteration_count.times do |i|

# i is number from 0-999
j = i + 1
# how many times the total number is divisible by 100 (I couldn't come up with a great name off the top of my head)
denominator = iteration_count / 100

  # add 1 percent every 10 times
  if j % denominator == 0
    progress << "="
    # move the cursor to the beginning of the line with \r
    print "\r"
    # puts add \n to the end of string, use print instead
    print progress + " #{j / denominator} %]"

    # force the output to appear immediately when using print
    # by default when \n is printed to the standard output, the buffer is flushed. 
    $stdout.flush
    sleep 0.05
  end
end
puts "\nDone!"