Any Function in Ruby determine the difference between folders level?

What I'm trying to do is to figure out if some folders is one of children / parents Or not related.

Is there any function in the Ruby File API? if not how to figure it out?

For example:

real_path_1 = "/Users/amr/Code/xx/zz"
real_path_2 = "/Users/amr/Code/"
# when I have to compare between these paths like:
f_level(real_path_1, real_path_2)
# it should return +2
# that means real_path_1 is **parent** of real_path_2
# with 2 levels depth

Also another example:

real_path_1 = "/Users/amr/Code/"
real_path_2 = "/Users/amr/Code/foo/bar/inside"
# when I have to compare between these paths like:
f_level(real_path_1, real_path_2)
# it should return -3
# that means real_path_1 is **child** of real_path_2
# w开发者_JS百科ith 3 levels depth

Another example:

real_path_1 = "/Users/amr/Code/"
real_path_2 = "/Users/amr/Code/"
# when I have to compare between these paths like:
f_level(real_path_1, real_path_2)
# it should return 0
# that means real_path_1 is **same level** as real_path_2

When returns nil:

real_path_1 = "/Users/other/Code/" # or "/folder2/"
real_path_2 = "/Users/amr/Code/" # or "/folder1/"
# when I have to compare between these paths like:
f_level(real_path_1, real_path_2)
# it should return nil
# that means real_path_1 is **not at same level** as real_path_2

def f_level a,b
    if a[/^#{b}/] && (b[-1,1] == '/' || $'[0,1] == '/')
        $'.scan(/[^\/]+/).size
    elsif b[/^#{a}/] && (a[-1,1] == '/' || $'[0,1] == '/')
        -($'.scan(/[^\/]+/).size)
    end
end

"/Users/amr/Code/xx/zz"
"/Users/amr/Code/"
2
"/Users/amr/Code/"
"/Users/amr/Code/xx/zz"
-2
"/Users/amr/Code/"
"/Users/amr/Code/"
0
"/Users/other/Code/"
"/Users/amr/Code/"
nil

Another idea without regular expressions:

def f_level(path1_string, path2_string)
  path1, path2 = [path1_string, path2_string].map { |s| s.split(File::SEPARATOR) }  
  minsize = [path1, path2].map(&:size).min
  path1.first(minsize) == path2.first(minsize) ? path1.size - path2.size : nil
end

raise unless f_level("/Users/amr/Code/xx/zz",  "/Users/amr/Code/") == 2
raise unless f_level( "/Users/amr/Code/", "/Users/amr/Code/foo/bar/inside") == -3
raise unless f_level("/Users/amr/Code/", "/Users/amr/Code/") == 0 
raise unless f_level("/Users/other/Code/", "/Users/amr/Code/") == nil