Futher refinement of Q9/A9.

man7/epoll.7

@@ -385,11 +385,18 @@ Receiving an event from
 .BR epoll_wait (2)
 should suggest to you that such
 file descriptor is ready for the requested I/O operation.
-You have simply to consider it ready until you receive the next
+You must consider it ready until the next (non-blocking)
+read/write yields
 .BR EAGAIN .
 When and how you will use the file descriptor is entirely up to you.
 .sp
-For stream oriented files (e.g., pipe, FIFO, stream socket), the
+For packet/token-oriented files (e.g., datagram socket,
+terminal in canonical mode),
+the only way to detect the end of the read/write I/O space.
+is to continue to read/write until
+.BR EAGAIN .
+.sp
+For stream-oriented files (e.g., pipe, FIFO, stream socket), the
 condition that the read/write I/O space is exhausted can also be detected by
 checking the amount of data read from / written to the target file
 descriptor.
@@ -402,11 +409,8 @@ can be sure of having exhausted the read I/O space for the file
 descriptor.
 The same is true when writing using
 .BR write (2).
-.sp
-For packet/token oriented files (e.g., datagram socket,
-terminal in canonical mode), you need to continue to read/write until
-.BR EAGAIN ,
-in order to detect the end of the read/write I/O space.
+(Avoid this latter technique if you cannot guarantee that
+the monitored file descriptor always refers to a stream-oriented file.)
 .SS Possible Pitfalls and Ways to Avoid Them
 .TP
 .B o Starvation (edge-triggered)