From: Lloyd Zusman <ljz@...>
Date: 2002-08-11T11:41:00+09:00
Subject: Re: Something that corresponds to Perl's -T and -B tests?

Lloyd Zusman <ljz@asfast.com> writes:

> ts <decoux@moulon.inra.fr> writes:
>
>>>>>>> "L" == Lloyd Zusman <ljz@asfast.com> writes:
>>
>> L> I've searched the Ruby documentation, and I can't find descriptions of
>> L> anything that corresponds to Perl's `-T' and `-B' tests ... these test
>> L> whether a file contains ASCII text or "binary" data, respectively.
>>
>>  See [ruby-talk:44936]
>
> [ ... ]
>
> I'll wait a day or so to see if someone reports any other currently
> written code, but if not, I'll write and post my own version here.

I've written an extension to File::Stat which adds a textfile? and
binaryfile? method.  Each works pretty much the same as the file?
and directory? methods of File::Stat.  For example:

  s0 = File.stat("/etc/fstab")
  s1 = File.stat("/bin/sh")
  s2 = File.stat("/tmp")

  p s0.textfile?   => true
  p s0.binaryfile? => false
  p s1.textfile?   => false
  p s1.binaryfile? => true
  p s2.textfile?   => false
  p s2.binaryfile? => false

It currently only works with File#stat, but eventually, I'd like to make
this work with IO#stat and File#lstat.

But before I do this work, I'd like the group's feedback on what I've
written so far.  Thanks in advance.

class File

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

  class Stat

  private

    def self.isText(block)
       return (block.count("^ -~", "^\b\f\t\r\n") < (block.size / 3.0) &&
	       block.count("\x00") < 1)
    end

  public

    alias_method :__old_initialize, :initialize

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

    # The textfile? and binaryfile? methods are not inverses of each
    # other.  Both return false if the item is not a file, or if the
    # item is a zero-length file.  The "textness" or "binariness" of
    # an item can only be determined if it's a file that contains at
    # least one byte.

    def textfile?
      if self.zero? then
        return false
      end
      begin
        open(@item) {
          |file|
          block = file.read(self.blksize < self.size ?
	                    self.blksize : self.size)
          return self.class.isText(block)
        }
      rescue
        return false
      end
    end

    def binaryfile?
      if self.zero? then
        return false
      end
      begin
        open(@item) {
          |file|
          block = file.read(self.blksize < self.size ?
	                    self.blksize : self.size)
          return !self.class.isText(block)
        }
      rescue
        return false
      end
    end

  end # class Stat

end # class File


-- 
 Lloyd Zusman
 ljz@asfast.com