Ruby

I din't have a windows machine right now so not sure this is the solution for you. But JFYI you can reroute the IOs by specifying arguments to spawn like this:

def exec(cmd)
  pid = Process.spawn(cmd, in: STDIN, out: STDOUT, err: STDERR)
  Process.waitpid pid
end

Using Process.spawn indeed works :) Unfortunately, I cannot figure out a way to forward the standard output and standard error to the console (i.e, STDOUT and STDERR) as well as storing that output in a variable.

The example in test.rb is a minimal example that just reproduces the issue where the subprocess does not receive any data on its standard input. But, the real code is a little bit more complex as it needs to store the output generated by the subprocess too.

Is there any easy way to do so? Is fork + exec and using pipes the only way to go?

system also accepts redirections.
And child processes inherit STDIN/STDOUT/STDERR from their parent process by the default, you don't need such arguments at all usually.
If you want to capture the outputs and the errors, IO.popen(%w'terraform destroy', err: [:child, :out], &:read).

Thanks for the suggestions.

The following code snippet based on IO.popen seems to work. It executes a command, and it returns its output as an array containing the output lines. Optionally, the output is written to stdout too.

def run(cmd, directory: Dir.pwd, print_output: true)
  out = IO.popen(cmd, err: %i[child out], chdir: directory) do |io|
    begin
      out = ''
      loop do
        chunk = io.readpartial(4096)
        print chunk if print_output
        out += chunk
      end
    rescue EOFError; end
    out
  end

  $?.exitstatus.zero? || (raise "Error running command #{cmd}")

  out.split("\n")
     .map { |line| line.tr("\r\n", '') }
end

I am not sure whether there is an easier way to accomplish this, but this seems good enough.