Description

   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.