pty.py 文件源码

def _open_terminal():
    """Open pty master and return (master_fd, tty_name).
    SGI and generic BSD version, for when openpty() fails."""
    try:
        import sgi
    except ImportError:
        pass
    else:
        try:
            tty_name, master_fd = sgi._getpty(os.O_RDWR, 0o666, 0)
        except IOError as msg:
            raise os.error(msg)
        return master_fd, tty_name
    for x in 'pqrstuvwxyzPQRST':
        for y in '0123456789abcdef':
            pty_name = '/dev/pty' + x + y
            try:
                fd = os.open(pty_name, os.O_RDWR)
            except os.error:
                continue
            return (fd, '/dev/tty' + x + y)
    raise os.error('out of pty devices')