FileTest.relative?

Ruby
1

It seems FileTest lacks a relative? method (and conversely absolute?). I need such a method. I went to write one but found my self not
100% certain about it being cross-platform. I wrote:

module FileTest
module_function

def relative?(path)
  /\A[\/\\]/ !~ File.expand_path(path)
end

end

To put it in English, I expand the path and then simply check for a
leading ‘/’ or ‘’.

I noticed Pathname has a relative? method and I looked at it. It’s
seems a bit bulky:

if File::ALT_SEPARATOR
  SEPARATOR_LIST = "#{Regexp.quote File::ALT_SEPARATOR}

#{Regexp.quote File::SEPARATOR}"
SEPARATOR_PAT = /[#{SEPARATOR_LIST}]/
else
SEPARATOR_LIST = “#{Regexp.quote File::SEPARATOR}”
SEPARATOR_PAT = /#{Regexp.quote File::SEPARATOR}/
end

def relative?
  path = @path
  while r = chop_basename(path)
    path, basename = r
  end
  path == ''
end

def chop_basename(path)
  base = File.basename(path)
  if /\A#{SEPARATOR_PAT}?\z/o =~ base
    return nil
  else
    return path[0, path.rindex(base)], base
  end
end
private :chop_basename

Is all that really necessary? My version may be too simplistic, but
surely there is more concise way to do this?

2

On Tue, Dec 21, 2010 at 3:35 PM, Intransition [email protected]
wrote:

It seems FileTest lacks a relative? method (and conversely absolute? ). I need such a method. I went to write one but found my self not
100% certain about it being cross-platform. I wrote:

Pathname has both #absolute? and #relative?, as well as some other
nice methods for figuring out what a path means. Maybe look there?

Ben

3

On Dec 21, 8:35pm, Intransition [email protected] wrote:

end

Is all that really necessary? My version may be too simplistic, but
surely there is more concise way to do this?

Your code is not contemplating drive letters.

4

On Dec 21, 6:52pm, Luis L. [email protected] wrote:

Your code is not contemplating drive letters.

Good point.

5

On Wed, 22 Dec 2010 09:06:04 +0900, Intransition wrote:

On Dec 21, 6:52 pm, Luis L. [email protected] wrote:

Your code is not contemplating drive letters.

Good point.

On Windows, a path without a drive letter that only starts in a single
backslash would be relative (becuase it’s relative to the current drive
letter.) A double backslash would be an absolute UNC name.