If the write is to an RMS record file and the buffer contains
    embedded new-line characters, more than one record may be written
    to the file. Even if there are no embedded new-line characters,
    if nbytes is greater than the maximum record size for the file,
    more than one record will be written to the file. The write
    function always generates at least one record.

    If the write is to a mailbox and the third argument, nbytes,
    specifies a length of 0, an end-of-file message is written to
    the mailbox. This occurs for mailboxes created by the application
    using SYS$CREMBX, but not for mailboxes created to implement
    POSIX pipes. For more information see the "Subprocess Functions"
    chapter of the VSI C RTL Reference Manual.