# open4status.rb: Spawn a program like popen, but with stderr, too. You might also
# want to use this if you want to bypass the shell. (By passing multiple args,
# which IO#popen does not allow).
#
# It returns an array of stdin, stdout and stderr IO objects. The fourth element
# it returns is a Process:Status object so you can determine the exit code
# of the program run.
#
# Usage:
#       require "open4status"
#
#      stdin, stdout, stderr, status = Open4.popen4status('nroff -man')
#  or
#       include Open4
#      stdin, stdout, stderr = popen4status('nroff -man')

module Open4
  #[stdin, stdout, stderr, status] = popen4(command);
  def popen4status(*cmd)
    pw = IO::pipe   # pipe[0] for read, pipe[1] for write
    pr = IO::pipe
    pe = IO::pipe

    pid = fork{
      # child
      grandchild_pid = fork{
        # grandchild
        pw[1].close
        STDIN.reopen(pw[0])
        pw[0].close

        pr[0].close
        STDOUT.reopen(pr[1])
        pr[1].close

        pe[0].close
        STDERR.reopen(pe[1])
        pe[1].close

        exec(*cmd)
      }
      grandchild_status = Process.waitpid2( grandchild_pid ).last
      exit!(grandchild_status.exitstatus)
    }
    pw[0].close
    pr[1].close
    pe[1].close
    status = Process.waitpid2(pid).last
    pi = [pw[1], pr[0], pe[0], status ]
    pw[1].sync = true
    if defined? yield
      begin
        return yield(*pi)
      ensure
        pi.each{|p| p.close unless p.closed?}
      end
    end
    pi
  end
  module_function :popen4status
end

if $0 == __FILE__
  a = Open4.popen4status("nroff -man")
  Thread.start do
    while line = gets
      a[0].print line
    end
    a[0].close
  end
  while line = a[1].gets
    print ":", line
  end
end