Given a path, how to determine if it's absolute/relative in Ruby?

Question

I am working on writing a rake build scrip which will work cross platform ( Mac OSX, Linux , Windows ). The build script will be consumed by a CI server.

I want the logic of my script to be as follows:

1. If the path is determined to be relative, make it absolute by making output_path = FOO_HOME + user_supplied_relative_path
2. If the path is determined to be absolute, take it as-is

I'm currently using Pathname.new(location).absolute? but it's not working correctly on windows.

What approach would you suggest for this?

Answer 1

require 'pathname'
(Pathname.new "/foo").absolute? # => true
(Pathname.new "foo").absolute? # => false

Answer 2

The method you're looking for is realpath.

Essentially you do this:

absolute_path = Pathname.new(path).realpath

N.B.: The Pathname module states that usage is experimental on machines that do not have unix like pathnames. So it's implementation dependent. Looks like JRuby should work on Windows.