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Count (group by) number of line occurrences in file

Here’s a neat ruby script to group and count the number of occurrences of lines inside a given file.

count.rb

list = IO.readlines(ARGV[0])
h = Hash.new {|hash, key| hash[key] = 0}
list.each {|item| h[item] += 1}
h = h.sort_by { |k,v| v }.reverse
h.each_with_index do |p,i|
  puts "(#{p[1]}) #{p[0]}"
  if ARGV[1] and ARGV[1].to_i <= i + 1
    break
  end
end

Usage is:

ruby count.rb <file> [show_at_most_n]

If you have a file named “faren.txt” comprised of the following lines:

test
test
awesome
dude
dude
dude
faren
meran

Running the script  with:

ruby count.rb faren.txt

Will yield the following result:

(3) dude
(2) test
(1) awesome
(1) faren
(1) meran

In addition, if you pass the “show_at_most_n” parameter (a number), it will only print that number of results. For example 2 will show the following:

(3) dude
(2) test

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Categorised as: ruby, software development, technology