From: "Jan E." <jan.e@...>
Date: 2012-03-06T04:18:06+09:00
Subject: Re: Inconsistent behaviour when working with a string

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.

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

You only do the processing if the file parameter matches the pattern you 
described earlier. While checking this, you save the timestamp substring 
in the first regex group (accessible by $1). You can then extract the 
year and month from the timestamp.

Your second example I don't really understand. You now assume that the 
file names begin with the timestamp, although the names should begin 
with "access" (that's what you said earlier). While this example won't 
throw any errors, it will generate nonsense output like "year = ac ..."

Jacques

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