Class AvoidUNCPath

IPython/utils/_process_win32.py:25–65

A context manager to protect command execution from UNC paths. In the Win32 API, commands can't be invoked with the cwd being a UNC path. This context manager temporarily changes directory to the 'C:' drive on entering, and restores the original working directory on exit. The conte

class AvoidUNCPath:
    """A context manager to protect command execution from UNC paths.

    In the Win32 API, commands can't be invoked with the cwd being a UNC path.
    This context manager temporarily changes directory to the 'C:' drive on
    entering, and restores the original working directory on exit.

    The context manager returns the starting working directory *if* it made a
    change and None otherwise, so that users can apply the necessary adjustment
    to their system calls in the event of a change.

    Examples
    --------
    ::
        cmd = 'dir'
        with AvoidUNCPath() as path:
            if path is not None:
                cmd = '"pushd %s &&"%s' % (path, cmd)
            os.system(cmd)
    """

    def __enter__(self) -> Optional[str]:
        self.path = os.getcwd()
        self.is_unc_path = self.path.startswith(r"\\")
        if self.is_unc_path:
            # change to c drive (as cmd.exe cannot handle UNC addresses)
            os.chdir("C:")
            return self.path
        else:
            # We return None to signal that there was no change in the working
            # directory
            return None

    def __exit__(
        self,
        exc_type: Optional[type[BaseException]],
        exc_value: Optional[BaseException],
        traceback: Optional[TracebackType],
    ) -> None:
        if self.is_unc_path:
            os.chdir(self.path)


def _system_body(p: subprocess.Popen[bytes]) -> int: