itting to the receiving
        program. As this is buffered, there is a limited size of such buffer.

        On Linux systems, this is 4096 (defined by N_TTY_BUF_SIZE). All
        other systems honor the POSIX.1 definition PC_MAX_CANON -- 1024
        on OSX, 256 on OpenSolaris, and 1920 on FreeBSD.

        This value may be discovered using fpathconf(3)::

            >>> from os import fpathconf
            >>> print(fpathconf(0, 'PC_MAX_CANON'))
            256

        On such a system, only 256 bytes may be received per line. Any
        subsequent bytes received will be discarded. BEL (``'