Write calls which do partial writes

[Doug Gwyn]

In article <103 at matrix.UUCP> neeraj at matrix.UUCP (neeraj sangal) writes:
>        n = write(fd, buf, len);
>    1. Can n be less than len if fd is NOT set to non-blocking?

Certainly; if only some but not all bytes were transferred,
for example due to the system call being interrupted by a signal,
then the best thing for write() to report is the number of bytes
successfully transferred.  (I forget whether IEEE 1003.1 ended up
permitting this or not; it was hotly debated.)  Robust stdio
implementations have to loop on the write() call until all bytes
are transferred or an error occurs.

>Will the underlying protocol complete select the moment a single
>byte can be transferred...?

Obviously it should.

The details depend on the exact implementation and are complicated
by things like the guaranteed pipe atomic write size, etc.