How to detect a process ending with Ruby open3

Question

If I run open with:

input, output,error = Open3.popen3 "nikto -host someip -port 80 -output xml"

How can I detect if nikto is done? It takes a while for the scan to complete.

If something goes wrong, I suppose I have to periodically check error to see if anything that been written?

Is there any decent docs that exist for open3? No, the ruby-docs are nowhere near decent.

Answer 1

input, output, error = Open3.popen3 "nikto -host someip -port 80 -output xml"

if select([output], nil, nil, 0.1) and output.eof?
  # process exited and doesn't have output queued.
else
  # still running or has output not read yet.
end

Also, here is some good documentation I found by googling: http://www.ensta.fr/~diam/ruby/online/ruby-doc-stdlib/libdoc/open3/rdoc/index.html

Answer 2

If you're using any *nix OS, your process will receive SIGCHLD when a subprocess exits. Depending on whether or not you have more than one subprocess at a time, this can be used to detect when it ends.

Also, the IO channels to the subprocess are implemented under the hood with pipes, so you will definitely get an EOF at the end of the output and possibly SIGPIPE when it shuts too.

In Ruby, installing a signal handler is just:

Signal.trap("CHLD") do
  Process.wait
  $child_died = true
end