Gotcha: DOS maintains CWD for each drive

gistfile1.md

Given this scenario:

K:\>dir
...
some_dir
job_1
...
K:\>cd some_dir
K:\some_dir> C:
C:\> cd script
C:\script> ruby processor.rb

You would expect this output...

In job job_1

Instead, we receive no output at all! Why?

Gotcha(s):

1. Changing drives in DOS/Windows is a separate action from changing the CWD for a drive.
2. Changing the working path to a different drive requires 2 steps.
3. When Dir.chdiring to a non-root path on Windows, Ruby combines these steps to be more Unix-like. When passed a root path, however, it defers to whatever DOS' CWD is stored. Unfortunately, when you change drives in a DOS/Windows environment, your CWD for that drive is remembered!

As a result, in the above scenario, changing dir to ROOT_PATH (which we know to be K:) actually changes dir to K:\some_dir!

Solutions: Add a trailing / to the ROOT_PATH variable.

processor.rb

ROOT_PATH = 'K:'

Dir.chdir(ROOT_PATH) do
  Dir.glob('job_*').each do |job|
    puts "In job #{job}"
    #... perform work within each job
  end
end

processor_fixed.rb

ROOT_PATH = 'K:'

Dir.chdir(ROOT_PATH + '/') do
  Dir.glob('job_*').each do |job|
    puts "In job #{job}"
    #... perform work within each job
  end
end