From: Brian Adkins <lojicdotcom@...>
Date: 2007-10-14T10:35:07+09:00
Subject: Re: top 10 last played mp3's

On Oct 13, 8:35 pm, "Andreas S." <x-ruby-forum....@andreas-s.net>
wrote:
> Konrad Meyer wrote:
> > Quoth Andreas S.:
> >> > know how to (correctly) compare a date to the return value of
>
> >> Dir['/share/music/**/*.mp3', '/share/music/*.mp3'].sort_by{|f|
> >> File.atime}.reverse[0,10]
>
> > Or, if it's deeper than two levels:
>
> '**' takes care of that.

Ah, you're right! I missed that also (even though the ** line is
highlighted in the pickaxe now that I bother to read Dir#glob :) ).

Before reading your explanation, I put the following together. It
might be a little friendlier for handling multiple extensions I
suppose, especially since the glob pattern isn't a real regex.

require 'pp'
require 'find'

def n_recent_files n = 1, path = '.', exts = nil
  paths = []
  Find.find(path) do |p|
    if File.file?(p) &&
       ( exts.nil? ||
         ( (ext = File.extname(p)) &&
           !ext.empty? &&
           exts.include?(ext) ) )
      paths << p
    end
  end
  paths.sort! {|a,b| File.atime(b) <=> File.atime(a) }[0,n]
end

pp n_recent_files(10, '/home/brian/temp', '.mp3')
pp n_recent_files(10, '/home/brian/temp', ['.mp3', '.ogg'])

Some notes for the OP:
1) Welcome to Ruby!
2) Enumerable#sort_by can be slow in some cases, and by using sort (or
sort! in this case), the comparison can be reversed to avoid calling
Array#reverse on the entire array later.
3) It exhibits a benefit of 'duck typing' since both String and Array
define include? the caller can pass in a single string or an array of
strings for the extension parameter w/ no extra effort in the
function.
4) Although the if expression is complicated, it has the advantage of
only computing the file extension when necessary.

Brian