cmd2.py 文件源码

def _redirect_output(self, statement):
        """Handles output redirection for >, >>, and |.

        :param statement: ParsedString - subclass of str which also contains pyparsing ParseResults instance
        """
        if statement.parsed.pipeTo:
            self.kept_state = Statekeeper(self, ('stdout',))

            # Create a pipe with read and write sides
            read_fd, write_fd = os.pipe()

            # Make sure that self.poutput() expects unicode strings in Python 3 and byte strings in Python 2
            write_mode = 'w'
            read_mode = 'r'
            if six.PY2:
                write_mode = 'wb'
                read_mode = 'rb'

            # Open each side of the pipe and set stdout accordingly
            # noinspection PyTypeChecker
            self.stdout = io.open(write_fd, write_mode)
            # noinspection PyTypeChecker
            subproc_stdin = io.open(read_fd, read_mode)

            # We want Popen to raise an exception if it fails to open the process.  Thus we don't set shell to True.
            try:
                self.pipe_proc = subprocess.Popen(shlex.split(statement.parsed.pipeTo), stdin=subproc_stdin)
            except Exception as ex:
                # Restore stdout to what it was and close the pipe
                self.stdout.close()
                subproc_stdin.close()
                self.pipe_proc = None
                self.kept_state.restore()
                self.kept_state = None

                # Re-raise the exception
                raise ex
        elif statement.parsed.output:
            if (not statement.parsed.outputTo) and (not can_clip):
                raise EnvironmentError('Cannot redirect to paste buffer; install ``xclip`` and re-run to enable')
            self.kept_state = Statekeeper(self, ('stdout',))
            self.kept_sys = Statekeeper(sys, ('stdout',))
            if statement.parsed.outputTo:
                mode = 'w'
                if statement.parsed.output == 2 * self.redirector:
                    mode = 'a'
                sys.stdout = self.stdout = open(os.path.expanduser(statement.parsed.outputTo), mode)
            else:
                sys.stdout = self.stdout = tempfile.TemporaryFile(mode="w+")
                if statement.parsed.output == '>>':
                    self.poutput(get_paste_buffer())