From: Robert Klemme <shortcutter@...>
Date: 2009-11-02T17:33:19+09:00
Subject: Re: mtime.max

2009/10/31 Paul Smith <paul@pollyandpaul.co.uk>:
> On Sat, Oct 31, 2009 at 1:38 AM, Derek Smith
> <derekbellnersmith@yahoo.com> wrote:
>> Hi All,
>>
>> My goal is to get the oldest file using mtime.to_i then delete it.
>> However my
>> puts stats.to_a.max does not seem to print out the oldest mtime
>> data/file, rather its printing out the 2nd to oldest file;
>> prod_db_bkup_Tue2009-10-271455.gz
>>
>> Correct me please and show me the code.
>>
>> thx!
>>
>> <snip>
>> d=Date.today
>> t=Time.now
>> require 'enumerator'
>>    stats = Hash.new
>>    DB_BKUP1.each do |dbfile|
>>        stats[dbfile] = [File.stat(dbfile).mtime.to_i]
>>    end
>>    puts stats.to_a,"\n\n"
>>    puts stats.to_a.max
>
> This line is sorting the hash by the key, i.e. the filename.  You'll
> see that Tue is alphabetically after Thu and Fr, and 271642 is after
> 271455.
>
> instead, try
>
> puts stats.sort {|x,y| x[1] <=> y[1]}.max
>
> This explicitly sorts by the 2nd value in the to_a array, which is the mtime.

There is no point in first sorting and then using max.  Only one of
the two makes sense: either you sort by your criterion and then take
the first or last OR you find the max or min according to your
criterion.

Kind regards

robert


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