How to get the caller path from Ruby/Rake?

Question

In Ruby/Rake(a gem for Ruby), current file path can be get through Dir.pwd and __FILE__ .

There are times I want to get the caller's path, like to figure out a relative path the caller provided which is relative to their path (but not relative to the path of the Rakefile).

An example

In a Rakefile from directory /home/me/workspace/proj :

# ...

task :foo do
  file_name = ENV['WHICH_FILE']

  # As I can not get the caller dir, give it the Rakefile dir instead
  caller_dir = Dir.pwd

  file_name = "#{call_dir}/#{file_name}" unless file_name&.match? /^\//
  puts File.read file_name
  # ...
end

# ...

If a caller provides the absolute path of the target file, no problem:

$ WHICH_FILE=/home/me/workspace/proj/suba/subb/subc/file.txt rake foo

If a caller in /home/me/workspace/proj provides a relative path, still no problem:

$ WHICH_FILE=suba/subb/subc/file.txt rake foo

If a caller in /home/me/workspace/proj/suba provides a relative path, the file_name may point to a wrong place:

$ WHICH_FILE=subb/subc/file.txt rake foo

Now file_name would be /home/me/workspace/proj/subb/subc/file.txt , which may not be what the caller want.

Questions

Is it possible to get the caller's path in Ruby/Rake? If it's possible, how?

Answer 1

You can tell where the user is right now, like you said, with Dir.pwd , but there's no way to guess which absolute path the user really wants.

This is why most scripts (or apps, etc) either have a ROOT_DIR that allows you to default to that as a prefix for the rest of the directory structure or just assume the file passed is under the current folder (shown by pwd).

Your choice is either set this ROOT_DIR somewhere in your code or just being open to the chance the user gives you a relative path to a file without really knowing what the absolute route to that file is and just assume is under their current dir.