Sporadic missing EOF for pty shell

README.md

Demonstrates a pecuilar problem whereby it appears a shell session occasionally does not produce an EOF on the pty slave after exit. I'm not sure this is an issue with the implementation of PTY or an OS X issue. It does not appear to be a shell issue per-se as I can produce the failure with bash, zsh, ksh, csh, and tcsh.

Example failures:

thinkerbot:~/Documents/Gems/shell_test> ruby --version
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.4.0]

thinkerbot:~/Documents/Gems/shell_test> time ruby pty_fail.rb 10000 /bin/bash
pty_fail.rb:19:in `block (2 levels) in <main>': timeout waiting for slave EOF (i:425 pid:13569) (RuntimeError)
"exit 8\r\n$ exit 8\r\nexit\r\n"
	from pty_fail.rb:9:in `spawn'
	from pty_fail.rb:9:in `block in <main>'
	from pty_fail.rb:8:in `upto'
	from pty_fail.rb:8:in `<main>'

real	0m4.323s
user	0m0.839s
sys	0m1.917s

thinkerbot:~/Documents/Gems/shell_test> time ruby pty_fail.rb 10000 /bin/ksh
pty_fail.rb:19:in `block (2 levels) in <main>': timeout waiting for slave EOF (i:1056 pid:14626) (RuntimeError)
"exit 8\r\n$ exit 8\r\n"
	from pty_fail.rb:9:in `spawn'
	from pty_fail.rb:9:in `block in <main>'
	from pty_fail.rb:8:in `upto'
	from pty_fail.rb:8:in `<main>'

real	0m10.645s
user	0m1.849s
sys	0m6.187s

thinkerbot:~/Documents/Gems/shell_test> time ruby pty_fail.rb 10000 /bin/zsh
pty_fail.rb:19:in `block (2 levels) in <main>': timeout waiting for slave EOF (i:8027 pid:30685) (RuntimeError)
"exit 8\r\n\e[1m\e[7m%\e[m\e[1m\e[m                                                                               \r\r\e[m\e[m\e[m\e[J$ \e[Ke\bexit 8\r\r\n"
	from pty_fail.rb:9:in `spawn'
	from pty_fail.rb:9:in `block in <main>'
	from pty_fail.rb:8:in `upto'
	from pty_fail.rb:8:in `<main>'

real	2m15.123s
user	0m34.373s
sys	1m9.930s

thinkerbot:~/Documents/Gems/shell_test> time ruby pty_fail.rb 10000 /bin/ksh
pty_fail.rb:19:in `block (2 levels) in <main>': timeout waiting for slave EOF (i:168 pid:30856) (RuntimeError)
"exit 8\r\n$ exit 8\r\n"
	from pty_fail.rb:9:in `spawn'
	from pty_fail.rb:9:in `block in <main>'
	from pty_fail.rb:8:in `upto'
	from pty_fail.rb:8:in `<main>'

real	0m2.157s
user	0m0.283s
sys	0m0.867s

thinkerbot:~/Documents/Gems/shell_test> time ruby pty_fail.rb 10000 /bin/csh
pty_fail.rb:19:in `block (2 levels) in <main>': timeout waiting for slave EOF (i:554 pid:31965) (RuntimeError)
"exit 8\r\n[b13924:~/Documents/Gems/shell_test] thinkerbot% exit 8\r\r\nexit\r\n"
	from pty_fail.rb:9:in `spawn'
	from pty_fail.rb:9:in `block in <main>'
	from pty_fail.rb:8:in `upto'
	from pty_fail.rb:8:in `<main>'

real	0m7.299s
user	0m2.046s
sys	0m3.970s

thinkerbot:~/Documents/Gems/shell_test> time ruby pty_fail.rb 10000 /bin/tcsh
pty_fail.rb:19:in `block (2 levels) in <main>': timeout waiting for slave EOF (i:410 pid:32786) (RuntimeError)
"exit 8\r\n[b13924:~/Documents/Gems/shell_test] thinkerbot% exit 8\r\r\nexit\r\n"
	from pty_fail.rb:9:in `spawn'
	from pty_fail.rb:9:in `block in <main>'
	from pty_fail.rb:8:in `upto'
	from pty_fail.rb:8:in `<main>'

real	0m5.819s
user	0m1.524s
sys	0m2.977s

pty_fail.rb

require 'pty'

#############################################################################
# $ ruby --version
# ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
# $ ruby pty_no_eof_example.rb 10000
# ..pty_no_eof_example.rb:35:in `block (2 levels) in <main>': timeout waiting for slave EOF (cmd: /bin/bash i:258 pid:37196) (RuntimeError)
#   from pty_no_eof_example.rb:23:in `spawn'
#   from pty_no_eof_example.rb:23:in `block in <main>'
#   from pty_no_eof_example.rb:21:in `upto'
#   from pty_no_eof_example.rb:21:in `<main>
#############################################################################
# $ ruby --version
# ruby 1.8.7 (2010-08-16 patchlevel 302) [i686-darwin10.4.0]
# $ ruby pty_no_eof_example.rb 10000
# ....................................................................................................
#############################################################################

max = ARGV.shift || 10000
shell = ARGV.shift || '/bin/bash'
timeout = 3

1.upto(max.to_i) do |i|
  exitstatus = nil
  PTY.spawn(shell) do |slave, master, pid|
    begin

      # exit as soon as possible
      unless IO.select(nil,[master],nil,timeout)
        raise "timeout waiting for master (cmd: #{shell} i:#{i} pid:#{pid})"
      end
      master.write("exit 8\n")

      # read to EOF
      while true
        unless IO.select([slave],nil,nil,timeout)
          raise "timeout waiting for slave EOF (cmd: #{shell} i:#{i} pid:#{pid})"
        end

        begin 
          c = slave.read(1)
        rescue(Errno::EIO)
          c = nil
        end

        if c.nil?
          break
        end
      end

      # Cleanup and capture the exit status to validate the exit worked
      Process.wait(pid)
      exitstatus = $?.exitstatus

    rescue PTY::ChildExited
      # Wait can cause a ChildExited error on 1.8.6 and 1.8.7 so handle it as
      # a normal exit route.  1.9.2 does not exit this way.
      exitstatus = $!.status.exitstatus

    rescue Exception
      # Cleanup on error - note PTY::ChildExited must be accounted for again
      Process.kill(9, pid)
      Process.wait(pid) rescue PTY::ChildExited
      raise
    end
  end

  unless exitstatus == 8
    raise "\nexpected exit status 8 but was #{exitstatus.inspect}"
  end

  if i % 100 == 0
    $stdout.print '.'
    $stdout.flush
  end
end
puts