# How to sort this array **URL:** \ **Category:** Ruby\ **Created:** [October 30, 2008, 10:15pm UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182 "2008-10-30T22:15:44Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 30, 2008, 10:15pm UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/1 "2008-10-30T22:15:44Z")
Hi, I have an array containing files names. How do I sort them so that I can get the expected results? Thanks, Li ############# files=[ “c:/ruby/self/2004/20.txt”, “c:/ruby/self/2004/3.txt”, “c:/ruby/self/2004/2.txt”, “c:/ruby/self/2004/10.txt”, “c:/ruby/self/2004/1.txt” ] expected results: [ “c:/ruby/self/2004/1.txt”, “c:/ruby/self/2004/2.txt”, “c:/ruby/self/2004/3.txt”, “c:/ruby/self/2004/10.txt”, ] “c:/ruby/self/2004/20.txt”, ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 30, 2008, 10:34pm UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/2 "2008-10-30T22:34:03Z")
Li Chen wrote: > Hi, > > I have an array containing files names. How do I sort them so that I can > get the expected results? > > Thanks, > > Li > > ############# > files=[ > “c:/ruby/self/2004/20.txt”, > “c:/ruby/self/2004/3.txt”, > “c:/ruby/self/2004/2.txt”, > “c:/ruby/self/2004/10.txt”, > “c:/ruby/self/2004/1.txt” > ] > > expected results: > [ > “c:/ruby/self/2004/1.txt”, > “c:/ruby/self/2004/2.txt”, > “c:/ruby/self/2004/3.txt”, > “c:/ruby/self/2004/10.txt”, > ] > “c:/ruby/self/2004/20.txt”, You get that result because in “2” \<=\> “10” the comparison is byte by byte and then “2” is \> “1”, so it aborts there with “2” being \> than “10”. What you want is called natural sorting. Googling for natsort and ruby you should get a few results. Regards Stefan ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 30, 2008, 10:44pm UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/3 "2008-10-30T22:44:27Z")
here is my code: C:\Users\Alex\>irb irb(main):001:0\> files=[ irb(main):002:1\* “c:/ruby/self/2004/20.txt”, irb(main):003:1\* “c:/ruby/self/2004/3.txt”, irb(main):004:1\* “c:/ruby/self/2004/2.txt”, irb(main):005:1\* “c:/ruby/self/2004/10.txt”, irb(main):006:1\* “c:/ruby/self/2004/1.txt” irb(main):007:1\> ] =\> [“c:/ruby/self/2004/20.txt”, “c:/ruby/self/2004/3.txt”, “c:/ruby/self/2004/2.txt”, “c:/ruby/self/ 2004/10.txt”, “c:/ruby/self/2004/1.txt”] irb(main):008:0\> irb(main):009:0\* irb(main):010:0\* files=files.sort\_by do|s| irb(main):011:1\* s.split(///)[-1].split(/./)[0].to\_i irb(main):012:1\> end =\> [“c:/ruby/self/2004/1.txt”, “c:/ruby/self/2004/2.txt”, “c:/ruby/self/2004/3.txt”, “c:/ruby/self/2 004/10.txt”, “c:/ruby/self/2004/20.txt”] irb(main):013:0\> I am not sure if it is the Rubyish way. Li ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 30, 2008, 11:32pm UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/4 "2008-10-30T23:32:19Z")
On Fri, Oct 31, 2008 at 06:14:51AM +0900, Li Chen wrote: > files=[ > “c:/ruby/self/2004/2.txt”, > “c:/ruby/self/2004/3.txt”, > “c:/ruby/self/2004/10.txt”, > ] > “c:/ruby/self/2004/20.txt”, files = files.sort\_by { |f| f[//(\d+).[^/]\*\Z/, 1].to\_i } There are several things to explain here: - The #sort\_by method calls the block on each element to produce a set of surrogate values to use as sorting keys. - The regular expression captures the series of digits between the last slash in a string and the following dot. - The [] method can be called on String in many ways, including passing a RegExp and an index. That form returns the capture of the appropriate index from matching the RegExp or nil if the RegExp does not match. - Calling #to\_i on the result means that it will either parse the captured sequence of digits as an integer or, if the RegExp fails, return 0. –Greg ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 30, 2008, 11:35pm UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/5 "2008-10-30T23:35:49Z")
- Li Chen [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) (22:14) schrieb: > “c:/ruby/self/2004/1.txt”, > “c:/ruby/self/2004/2.txt”, > “c:/ruby/self/2004/3.txt”, > “c:/ruby/self/2004/10.txt”, > “c:/ruby/self/2004/20.txt”, > ] files.sort\_by { | fn | fn.match(/(\d+).txt$/)[1].to\_i } mfg, simon … hth ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 31, 2008, 5:02am UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/6 "2008-10-31T05:02:29Z")
On Fri, Oct 31, 2008 at 5:14 AM, Li Chen [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > expected results: > [ “c:/ruby/self/2004/1.txt”, > “c:/ruby/self/2004/2.txt”, > “c:/ruby/self/2004/3.txt”, > “c:/ruby/self/2004/10.txt”, > “c:/ruby/self/2004/20.txt”, > ] apology in advance for dupl email. i sent an email an hrs back but it seems it got blackholed 🙂 anyway, if you want basename numeric sorting, then just do eg, files.sort\_by{|f| File.basename(f).to\_i} ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 31, 2008, 9:13am UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/7 "2008-10-31T09:13:25Z")
2008/10/31 botp [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > seems it got blackholed 🙂 > > anyway, if you want basename numeric sorting, then just do > > eg, > > files.sort\_by{|f| File.basename(f).to\_i} Very elegant! Here’s another variant irb(main):013:0\> puts files.sort\_by {|f| f[/\d+(?=.txt$)/].to\_i} c:/ruby/self/2004/1.txt c:/ruby/self/2004/2.txt c:/ruby/self/2004/3.txt c:/ruby/self/2004/10.txt c:/ruby/self/2004/20.txt =\> nil Kind regards robert ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 31, 2008, 9:15am UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/8 "2008-10-31T09:15:11Z")
And here’s a variant for cases where there are multiple subdirectories: irb(main):010:0\> puts files.sort\_by {|f| f.scan(/\d+/).map{|x|x.to\_i}} c:/ruby/self/2004/1.txt c:/ruby/self/2004/2.txt c:/ruby/self/2004/3.txt c:/ruby/self/2004/10.txt c:/ruby/self/2004/20.txt Kind regards robert ---
**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\ **Post date:** [October 31, 2008, 2:24am UTC](https://www.ruby-forum.com/t/how-to-sort-this-array/152182/9 "2008-10-31T02:24:56Z")
On Oct 30, 2008, at 6:34 PM, Simon K. wrote: > > expected results: > > mfg, simon … hth > > Since #to\_i will stop at a non-digit, you could get simpler: files.sort\_by {|fn| fn[%r{.\*/([^/]+)},1].to\_i } I tend to use %r{ } when the Regexp deals with / characters. -Rob Rob B. [http://agileconsultingllc.com](http://agileconsultingllc.com) removed\_email\_address@domain.invalid