Class: Wopen3::Opener

Inherits:
Object
  • Object
show all
Defined in:
lib/wopen3.rb

Constant Summary collapse

READ =
0
WRITE =
1

Instance Method Summary collapse

Constructor Details

#initialize(*cmd) ⇒ Opener

Returns a new instance of Opener


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# File 'lib/wopen3.rb', line 36

def initialize *cmd
  write_pipe  = IO::pipe
  read_pipe   = IO::pipe
  error_pipe  = IO::pipe

  pid = fork do
    # in child
    write_pipe[WRITE].close
    STDIN.reopen(write_pipe[READ])    # file descriptor duplicated here
    write_pipe[READ].close            # must close in order for parent to
                                      # see EOF
    read_pipe[READ].close
    STDOUT.reopen(read_pipe[WRITE])
    read_pipe[WRITE].close

    error_pipe[READ].close
    STDERR.reopen(error_pipe[WRITE])
    error_pipe[WRITE].close

    exec(*cmd)  # will raise SystemCallError if command can't be executed
                # (eg Errno::NOENT)
    exit!       # should never get here
  end

  # in parent
  write_pipe[READ].close
  read_pipe[WRITE].close
  error_pipe[WRITE].close

  pipes = [write_pipe[WRITE], read_pipe[READ], error_pipe[READ]]
  write_pipe[WRITE].sync = true

  if defined? yield
    begin
      result = yield(*pipes)
      Process.waitpid(pid) # global $? gets set here
      return result
    ensure
      pipes.each { |pipe| pipe.close unless pipe.closed? }
    end
  end

  # can't wait immediately (will hang); wait once garbage collection
  # destroys/finalizes this instance
  ObjectSpace.define_finalizer(self, proc { Process.waitpid(pid) })
  pipes
end