From: Ryan Davis <ryand-ruby@...>
Date: 2007-08-11T13:19:25+09:00
Subject: Re: Sorting a logfile, how would you write it?


On Aug 10, 2007, at 13:54 , William James wrote:

> On Aug 10, 1:29 pm, Frank Meyer <lolz.ll...@gmail.com> wrote:
>> I've written a little ruby program which can sort logfiles with the
>> following format:
>>
>> 4.text text text
>> 1.text text text
>> 2.text text text
>> 10.text text text
>> 2.text2 text2 text2
> ...
> File.open( ARGV.first, "r+" ){|file|
>   array = file.readlines
>   file.rewind
>   file.truncate(0)
>   file.puts array.sort_by{|s| s[/^\d+/].to_i }
> }

your version takes a lot of memory, is slow, and doesn't properly  
sort the content of the line, just the number. swap the two "2."  
lines and you'll see what I mean. Using the right tool for the job  
(`sort`) does wonders:

% ruby -e 'n = 1_000_000; File.open("blah.txt", "w") { |f| n.times  
{ m = rand 5; f.puts "#{rand n}. file#{m} file#{m} file#{m}" } }'
% cp blah.txt blah2.txt
% time ruby -e 'File.open( ARGV.first, "r+" ) { |file| array =  
file.readlines; file.rewind; file.truncate(0); file.puts array.sort_by 
{|s| s[/^\d+/].to_i } }' blah.txt
real    0m8.182s ...
% time ruby -e 'path = ARGV.shift; system %(sort -n "#{path}" > "# 
{path}.tmp"); File.rename "#{path}.tmp", path' blah2.txt
real    0m3.175s ...
% cmp blah.txt blah2.txt
blah.txt blah2.txt differ: char 50, line 3
% head blah.txt blah2.txt
==> blah.txt <==
3. file4 file4 file4
4. file4 file4 file4
6. file3 file3 file3
6. file1 file1 file1
6. file0 file0 file0
7. file0 file0 file0
7. file4 file4 file4
8. file1 file1 file1
8. file3 file3 file3
8. file3 file3 file3

==> blah2.txt <==
3. file4 file4 file4
4. file4 file4 file4
6. file0 file0 file0
6. file1 file1 file1
6. file3 file3 file3
7. file0 file0 file0
7. file4 file4 file4
8. file1 file1 file1
8. file3 file3 file3
8. file3 file3 file3
532 %