From: Robert Klemme <shortcutter@...>
Date: 2012-03-06T18:42:29+09:00
Subject: Re: Inconsistent behaviour when working with a string

Jan E. wrote in post #1050236:
> Hi,
>
> The Dir.foreach iterator always begins with the current directory '.'
> and the parent directory '..'. If you don't skip these cases, the
> iterator will throw an error on the first run:
>
> If file is '.', then file[/\d{10,}/] is nil (there aren't any digits).
> And if fileint is nil, then fileint[0,2] will fail, because nil doesnt
> have a [] method.
>
> You should generally check the file parameter before processing it.
> Otherwise, you will always run into trouble if there are any entries
> that don't match the pattern.
>
> For example, you could write
>
> Dir.foreach(".") do |file|
>   if file =~ /access(?:_denied)?(\d+)\.merged\.log\.bz2/
>     timestamp = $1
>     year, month =
>       timestamp[0, 2], month[2, 2]
>     month = $months[month.to_i - 1]
>     puts "year = #{year} month = #{month} and file was #{file}"
>   end
> end

Absolutely!  I'd go just a bit further and make the matching more 
rigorous and also extract all relevant data in one go:

Dir.foreach(dir) do |file|
  if file =~ 
/\Aaccess(?:_denied)?(\d{2})(\d{2})\d{6}\.merged\.log\.bz2\z/
    year = $1.to_i
    month = $2.to_i
    puts "year = #{year} month = #{$months[month - 1]} and file was 
#{file}"
  end
end

Note: if there is a hierarchy of folders then also Find.find or 
Pathname.find could be used.

Kind regards

robert

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