From: Bertram Scharpf <lists@...>
Date: 2007-07-10T22:10:47+09:00
Subject: Re: Method to prevent writing over a file

Hi,

Am Dienstag, 10. Jul 2007, 22:03:52 +0900 schrieb Bertram Scharpf:
>
>       def safe_open name
>         i = 0
>         n = name
>         begin
>           f = File.new n, File::CREAT|File::EXCL|File::WRONLY
>           yield f
>         rescue Errno::EEXIST
>           i += 1
>           n = "#{name}_#{i}"
>           retry
>         ensure
>           f.close
>         end
>       end

Sorry, this is wrong. The yield should _not_ appear inside
the begin-rescue block as it could raise an exception
itself. Better is:

  def safe_open name
    i, n = 0, name
    f = begin
      File.new n, File::CREAT|File::EXCL|File::WRONLY
    rescue Errno::EEXIST
      i += 1
      n = "#{name}_#{i}"
      retry
    end
    yield f
  ensure
    f.close
  end


Bertram


-- 
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de