From: Lloyd Zusman <ljz@...>
Date: 2002-08-10T03:56:48+09:00
Subject: Re: Getting the file name from a File::Stat object?

GOTO Kentaro <gotoken@notwork.org> writes:

> At Fri, 9 Aug 2002 23:24:41 +0900,
> Lloyd Zusman wrote:
>> For that purpose, I know I can always use a subclass, like this:
>> 
>> [ ... etc. ... ]
>
> You can redefine File.stat as follows, however, I don't recommend this
> because File::stat is not API for a file but just for a inode.  For
> example, File::stat can represent a file which has been deleted already.
>
>  [ ... etc. ... ]

I totally agree with you, in the general case for the use of File::Stat.
However, I have a specific need for ANY of the valid filenames that
refer to the inode in question.  It doesn't matter which of the names I
use, as long as it's ONE of them.

I want to use that name in order to implement a "File::Stat#textfile?" 
method that returns true if the item in question is a file which
contains non-binary data.  In order to implement the "textfile?" method,
I have to have a filename that I can pass to an "open" method call,
as follows:

  class File

    def self.stat(arg)
      Stat.new(arg)
    end

    class Stat

      alias_method :__old_initialize, :initialize
      attr_reader :item

      def initialize(arg)
        @item = arg
        __old_initialize(arg)
      end

      # New method that returns "true" if the item is a file
      # that only contains text data (i.e., non-"binary" data).

      def textfile?
        begin
          open(@item) {
            |file|
            block = file.read(self.blksize < self.size ?
                              self.blksize : self.size)
            return block.size == 0 ||
                   ((block.count("^ -~", "^\b\f\t\r\n") / block.size) < 0.3 &&
                    block.count("\x00") < 1)
          }
        rescue
          return false
        end
      end

    end
  end

  s = File.stat("/etc/fstab")
  t = File.stat("/bin/sh")

  p s.textfile?    # outputs `true'
  p t.textfile?    # outputs `false'



-- 
 Lloyd Zusman
 ljz@asfast.com