Search code examples
jrubyttynailgun

/dev/tty opens in nailgun-server terminal

Given a sample script that opens /dev/tty:

# sample.rb
tty=File.open("/dev/tty", "w+")
tty.print "> "
tty.puts tty.gets.upcase

I can run it with normal jruby just fine:

% jruby sample.rb
> hello
HELLO
%

However, if I try to use /dev/tty with nailgun, then the tty is bound to the nailgun server, not the client:

# server terminal                                     | # client terminal
% jruby --ng-server                                   |
NGServer 0.9.1 started on all interfaces, port 2113.  |
                                                      | % jruby --ng sample.rb
> hello                                               |
HELLO                                                 |
                                                      | %

(the vertical spacing is to show timing, the actual output for each lacks the blank lines)

Is this expected behaviour, or a bug?

If it's expected behaviour, is there a way I can detect whether a script is being run with --ng so I can avoid opening /dev/tty?

Solution

  • Looking at the Nailgun client/server protocol, it doesn't look like it supports what would need to happen to use the client's /dev/tty (have client open a file, read/write from client to server).

    Whether it's a bug or not, it's outside the capabilities of Nailgun currently.

    Detecting whether we're on a Nailgun server can be done via

    # true if on a nailgun server, false elsewise
system("ps -fp #{Process.pid} | grep NGServer > /dev/null")