Question

I try to pipe the output from a command line command through Ruby.
It works fine but the coloring is missing.
How can I preserve the coloring?

This is what my code looks like:

cmd = "cucumber #{ARGV.join(" ")}"
IO.popen(cmd) do |io|
  io.each { |s| print s }
end

Updated:
The premise of the question was wrong – IO.popen does preserve the colors.

Answer 1

Run cucumber with the -c option. Otherwise cucumber determines that the terminal (the pipe) does not support coloring and will drop it if not explicitly forced on with -c.

https://github.com/cucumber/cucumber/blob/master/lib/cucumber/cli/options.rb#L211

...
opts.on("-c", "--[no-]color",
        "Whether or not to use ANSI color in the output. Cucumber decides",
        "based on your platform and the output destination if not specified.")
...